The second time is much easier because you can put the hardship in perspective. The first time around there is a lot of uncertainty and self-doubt -- you've never had to deal with the issues before -- and you tend to imagine the bad parts being far worse than they actually are. While it is still hard, the certainty of "been there, done that" greatly reduces the psychological stress in my experience.

Also, being able to anticipate the hardship in concrete terms also allows you to get in front of it and mitigate the adverse effects. You make fewer mistakes, so less of the hardship is self-inflicted.

Entrepreneurship is very difficult even in the best of circumstances, but it is also a skill and experience makes the job significantly easier.