Ask HN: How did you decide what problems to solve in your lifetime?

Ask HN: How did you decide what problems to solve in your lifetime?
In other words, how do you decide between what you want to work on and what should be worked on? I've been stuck with trying to figure what to do with the rest of my life. I can't decide whether I should be working on what I want to work on (Energy, AI) or whether I should work on what I believe should be worked on (Healthcare). It's a short life, so I want to be careful with this decision, to avoid any future regrets. Because I can't decide on this, I end up not getting anything done. Time continues to march on, while I'm still stuck with not knowing what to do. Has anyone had any experience with this before? If yes, then what and how did you make your decision? What was the outcome? Is there a middle ground or silver lining, where you managed to work on both cases?