Very similar situation here, turning 27 in September. Spent most of highschool skipping so I could write code instead. No friends nowadays (I prioritize everything else), no serious relationships (no time/energy), never traveled outside USA (money!).

I did, however, just leave a job where I was unhappy. The timing was not great and it cost me. But I couldn't be happier to be free of that job. When I started to seriously dread going in to work, I knew it was time to move on.

Try to realize that not leaving a job because you "can't stand disappointing anyone" is just plain wrong. In a sense, you're doing them a disservice by remaining in a position you are not happy in. You are probably not performing at your best if you're unhappy. Plus, startup or not, they would probably drop you like a bad habit if given the financial incentive. Business is business, money is always the bottom line in that environment. You do not owe them anything.