How do you know if you are doing the right thing or wasting a lot of time, when you could have just take a FAANG job and live a comfortable life?
Before success, anything is a calculated risk, and the success depends as much on your hard work and dedication and BELIEF in the idea, as it does in whether that belief is actually correct, and, since no one has done it before, it is unknown.
Comfortable life is whatever makes you comfortable, be it working hard on something you want to try, or working at a company and be relatively certain of a good income.
Lean startup methodologies might be useful in that regard.
As for the comfortable life - if that’s your goal then don’t do startups. You’ll quit 9-5 to work 24/7 with no guarantee… you only hear about those who crossed the chasm, it’s a selection bias that make most people have romanticized view of startups.
Evidence also suggests that careful contemplating (and getting competent feedback) what worked/didn't work, can help your next ticket be slightly more lucky than the last as you build new skills.