This is an oldishkindasorta topic. But I'll go ahead and say what I have to say.
I've contemplated suicide. I've been moments away from attempting it, but I've never gone through with it. Usually my justification was that I was simply a waste, that there wasn't a reason for me to be here so it would be fine if I offed myself. The fact that nobody tried to stop me really didn't make that justification any flimsier. At this point, I've actually decided that my life truly does have no meaning. That I'm just going to be here, breath some air and consume some matter, then be thrown into the ground with a few people watching (half of them probably random kids sitting there wondering who the hell "Uncle Keyguy" was). One reason I haven't killed myself is mainly because I've learned to really immerse myself into fiction. Sure, I'll never even leave the atmosphere, but I can read, write, and watch stories about people going to other stars and meeting alien lifeforms. Aside from extreme escapism (Not always a bad thing, mind you), there's one other reason:
(Dude, I didn't even make that. That's from google images. It's even exactly what I had in mind. This is amazing.)
So, not flat-out, Yes I Can Be Perfectly Described By This One Label Existentialism, but more or less close to it kindasortaish. Basically, I think that there's no meaning to my life, so I get to come up with my own meaning. Or meaning
s. Doesn't have to be just one if you ask me. I chose my writing, among other things. And it was surprisingly helpful. If there's nothing you can come up with, then there's no problem. I'm just really good at inflating the potential values of things and making a post-apoc dieselpunk story seem like the difference between the survival of the human species and it's extinction.
Combined with all of this is my idea that no matter what you do, it has incredible meaning. Basically the butterfly effect, to be honest. The way I see it, there might be someone who shows a tiny act of kindness towards someone. Maybe they just stopped for a moment to help clean up a mess, or maybe they just complimented their hair. That person they helped out? Maybe they were feeling like nobody really felt their existence, and maybe that one thing made them decide to go on living for just one day. And maybe, that next day, they'll give some money to someone else in a similar situation. Maybe the "Thank you" makes them decide to go on, and that tiny donation makes that someone else realize that someone else out there cares about them. Perhaps the two become friends, and they both decide that they should go on. I don't know if this helps anyone here, but just remember that there's always a reason you can find to go on living.