Be prepared to deal with a lot of BS for your startup.
At annual tech conference South by Southwest he told the audience:
"Think about the sacrifice, and think about all the [crap] that you will have to go through. Think about the very low probability of success, and think about the toll it will take on your family and everyone around you.
"It's almost a heroic effort, and it goes against the set ways of doing things. Think about losing friends, and think about a lot of things that will happen. Losing friends for sure, because you will have to be fiercely competitive, maybe with some of your friends. You have to start not liking people you have to compete with because you have to really motivate your team to be tough in this environment.
"I think it is slightly un-human to do that sort of venture, and I think all that should go into consideration."