The thing about dying in Libya or Syria or similar is that you die participating in something with historical significance. Living a very normal life elsewhere does not.
Given that Facebook and other social media were enablers for the Arab Spring, I would say that the average programmer at Facebook has about as much influence on the course of things as you would if you were to go put your life on the line over there.
I won't deny that "dying for the cause" is glamorous, but it doesn't mean jack shit. The vast majority of people who put their lives on the line in conflicts are
disposable, and the qualities of generals and leaders (who usually shield themselves from danger) are much more relevant than that of soldiers.
Take a look at
this. All those people are dead, but in death they've done more than 99.99% of the people in the world.
You could say the same about the smaller group of Nobel laureates, whose work did not imply a risk of death (save for radiation poisoning). These people did more than 99.99% of the people in the world because they had the relevant competences and courage to perform critical operations, not because they died.
My point is, somebody has an impact (good or bad) in proportion of how different (better or worse) the world would be without them. As it turns out, the impact of any given individual is extremely limited. The presence of absence of any given soldier will rarely make any difference, regardless of what they do, because they can only cover a limited part of the battlefield. The general planning out the operations is always the person with the most impact. Science and technology is always very incremental and a lot of discoveries are done independently by several people, because they just the next logical step at that point. We can't say that without Einstein relativity would not have been discovered: for one, the math was already there, and somebody else would have had the same insight eventually.
That might not be obvious at first glance, but if you want to maximize your *personal* impact on the world, Art (literature, film, architecture, painting, etc.) is probably your best bet. Philosophy is always reinvented, science and technology follow their own incremental pace, the effects of any war are undone by the next, the effects of any politicians are undone by the next, and so forth. Art is pretty much the only thing that a single man or woman can do and yet can endure for ages, as long as crazy people don't destroy it for petty reasons (which, sadly, they often do). It's a piece of their mind and an embodiment of their culture at the same time, that people can still enjoy millennia later. It sure won't survive the heat death of the universe but goddamn you are looking way too far in the future.
No, mortality isn't preventing me from doing anything. But it's stopping me from seeing purpose in many of the things in life. Right now my life is comfortable. My financial position is quite secure, I have most things I wish for (although I wish I had a million dollars, and I don't), in one perspective I'm happy. But from another perspective, my life is a complete and utter failure, and I could've done or be doing so much more to make it more colourful. I'm going to die, but if I die now, who will remember me?
I think you are putting too great emphasis on legacy, and unless you are 70, you are not dying anytime soon, so you have plenty of time to be happy about your life.
So here goes:
If you want to have an impact for eternity or for billions of years, you're insane. Get your shit together and lower your goddamn standards.
If you want to have an impact for millenia, you will need to write or build something truly epic and groundbreaking and then cross your fingers for somebody to notice. That's unbelievably difficult, partly out of your control, and competition is at an all-time high. You can also become a mad emperor and command batshit insane funerary buildings for yourself (pyramids or terracotta armies). I'll let you think about how difficult that is, and ponder how much of a hindrance to progress that also is.
If you want to have an impact for decades, that's not too unreasonable, but the most important thing is to get noticed. You'll need either great talent, great luck, or great people skill to stand out from the lot.
I think you are seeing the pattern here: making an impact on society is
fucking hard. Take any given length of time, multiply it by a thousand, take the inverse, and you'll get the fraction of people whose impact will last that long, and the worst thing of all is that these people's impact was partly due to
luck. The direct consequence of this is that if you care about impact or being remembered,
you are doomed to be miserable, not only because you won't succeed, but especially because even if you do, you won't know it before you're dead (especially true of painters).
Now, consider what you could care about instead:
Knowledge! Trying to figure out how the world works, contribute a tiny bit to science and mathematics, and have the satisfaction of finding the solution to problems. Take any non-trivial unsolved problem. There are millions of these, and thousands that many people care about. Now solve it. Chances are, that was difficult. Chances are, some people will look at your solution and tell you "nice! I didn't think about doing it that way!". That feels great! A good 5% of the population has the ability to do this.
Expression! Putting your ideas and feelings into words, into colors on canvas, into indie movies, into webcomics, into improvisation groups, into renovating and decorating your own home, into a garden. At least half of all people on the planet can do really cool stuff if they try. Expressing yourself is as easy as it has ever been. Fucking anybody can get thousands of hits on YouTube if they TRY. And it is FUN. I can't believe you can't find at least one thing you'd have fun doing that would leave you with the happy feeling of accomplishment. I know people who are mediocre at writing, but they still write, and they like to write, and it validates their existence, and you know what? They get better! Heck, right now, we live in a truly
blessed period, where anyone can put anything on the Net and have it automatically saved and archived on countless computers. Maybe in a thousand years, somebody will browse the Internet Archive on their HyperMac and will stumble across what you did, and they'll get some amusement out of it. That sure as hell won't happen if you don't do anything, and you are in the unique position to DO something, RIGHT NOW, within DAYS of reading this post. Your ancestors did not have this luck.
Just plain fun! read books, watch movies, play sports, travel all around the world, you know, just enjoy life. ANYBODY can do this. It doesn't take a lot of money to enjoy life, and if you don't have the time to enjoy life, you're doing something seriously wrong.
I'm sorry for the tl;dr, but seriously,
stop caring about legacy or impact. There are so many ways to be happy without caring about legacy that it would be a shame to have a miserable life just because you have the wrong priorities. In particular, if you truly care about knowledge and expression for their own sake, you will have a greater impact than if you only care about what you'll leave to the world. Legacy is always incidental. It's almost never something you plan, because planning legacy will leave you second thinking everything you do, and then you will do nothing at all.
@above - take my word for it when I say it won't. I have a background in physics, and by the second law of thermodynamics, all life must end when the universe is close to maximal disorder. You are a highly ordered being, but only because you consume food. You need energy. Almost everything on Earth gets its energy directly or indirectly from the Sun, but the Sun will not last forever. Eventually all the suns in the universe will burn out, and there will be no more life. Like it or not, you are mortal, and have no chance of escaping that fact.
Reversible computing is a potential escape route from the second law of thermodynamics, though it seems nigh impossible to implement in practice (basically, if every single computation you make is reversible, it is unknown if there is any physical limit to how little energy you can consume, and it could actually be as little as zero; all we know is that it's not doable with irreversible computation). In any case, it is theoretically possible to survive for a
long ass time, and I can't say I give a shit if I'm going to die a billion years from now. That would just be wayyy too far away for me to care yet.