Life isn't all for nothing, but it can be hard to see that sometimes.
I don't know what your circumstances are but I do know one thing. Terrible things do happen, and to a lot of people. I think some people are just naturally primed towards feeling bad when things are terrible, and feeling better when things are better. I don't think you should feel bad for feeling the way you do, to be clear, but I think a good way of looking at it is to appreciate the good times when they happen.
I can definitely empathize with that feeling of having good times soured by the knowledge that those good times are only temporary and you can't always stop the bad moments from breaking up the chain of good moments. I think that comes from having depression, or if not depression then maybe just some form of temporary irrationality, which again you shouldn't feel bad for, because one thing I've basically been trying to learn and re-learn is that most people have and deal with irrational thoughts and that no one person is perfectly rational.
Another thing. If that's truly the case that people care for you when you're not around, then they must care for you when you are around, maybe a bit too secretly.
I can say that from experience because I'm not very good at reaching out and talking to people, and someone who mattered a lot to me... Well, isn't around anymore. There's so much guilt and regret that comes with that.
Which isn't to tell you not to do something just because it will make other people feel guilty, but it's good to be aware of why they would feel guilty. They would feel guilty because they love and care about you and they would probably feel that they didn't express it enough.
Feel free to talk more about your life or experiences here, good and bad. Maybe there's some advice I or someone else can give related to that.
I'm sorry you're feeling this way and I hope you will feel better soon.
Stop trying. Take long walks. Look at scenery. Doze off at noon.
Don't even think about flying.
And then, pretty soon, you'll be flying again.