I've had seven heart attacks, a below-knee amputation, and I'm on dialysis for kidney failure, and I'm 51. I also had a saddle pulmonary embolism in 2017 that kills most people that have them, so I'm already living on "borrowed time" as it were. I'll link you to my story if you're curious, but anyway… I'm likely to last less than another decade, I think. And that sucks, but c'est la vie.
Here's what I live for:
- I take every day for that day. I try not to live in the past because I cannot change it. I try not to excessively dream about the future because I may not have one. I just try to live today for today. Now, I'm doing PT and exercises to try and increase health, so that is doing something for my future, but i'm not just wasting today dreaming about tomorrow. I'm trying to live today.
- I try to find things I enjoy doing because I enjoy them - playing some games, browsing the internet, reading. And I try to take pleasure in those things.
- I try to keep up with chores as I battle anemia and fatigue. I try to keep the household running as I'm able to help, trying to minimize what I depend on my partner for.
- Most importantly: I try to make those I come in contact with smile a little. I've always been like this, but I figure if I can make someone's day a little brighter, that's always a Good Thing™.
- I try not to worry too much about it.
We read about people who Made History™ and who were Important People™, but the extreme vast majority of people were born, grew up, worked and lived their lives, and died and were forgotten. And that's okay! Once you're gone, there won't be a you to worry about anything!
There is no goal to life other than to live it. But if you can, while taking care of yourself, do a little good in some way: That is worth doing.
So make sure you're doing things that are fulfilling, and try to worry less about comparing yourself to some sort of super-human you could never live up to - especially not some fictionalized superhero that doesn't even exist.
I'm completely atheist these days, but I still like the Wiccan Rede's version of what many more might know as the Golden Rule: "An' it harm none, do as ye will." This opens you up to being free to doing anything that doesn't cause harm. But an important thing to consider: Not only do not do harm to others, but do not do harm to yourself.
And one subtle self-harm is putting all your energy into worrying about some sort of legacy and trying to live up to artificial responsibilities at the expense of enjoying life. So don't do that.
Introspection is good. Thinking about these things is good. Just don't let thinking about it take over.
If you still feel like you should be doing "more", finding a place to put energy into volunteering is probably the answer. Find a cause you can believe in and think is valuable. You could mentor others - younger or old on whatever topics you're comfortable with. You could volunteer at an animal shelter. Or in the arts. Or any number of places that always need people helping out.
Don't limit yourself by thinking it has to be big to be helpful.