Everyone says: "No one on their deathbed regrets not spending more time at the office". Perhaps that's true. But I bet there are people who, on their deathbed, regret not having been more able to provide their families with financial security, or not doing a better job on something important they worked on.

You might die tomorrow. But it's more likely that you won't, and you should plan accordingly.

(I am not arguing that today's culture of overwork isn't harmful. I think it is, and I think most people in tech startups should probably be spending less time working. And if that what-if-I-died-tomorrow question is what it takes to get someone to think about what they really want to be doing with their lives, that's great. But it's still something of a cheat, and if you draw the conclusion from it that you should be optimizing your life for minimal regret on premature death then I think you're probably making a mistake.)