You can prevent many (but not necessarily all) of the adulthood regrets if you think ahead and plan ahead.
You don't have to gain weight. Just suck it up get up early and run 5 miles each morning.
You don't have to go through divorce. Marry the right girl for the right reasons. And if you truly try to take care of you, usually she'll reciprocate happily.
You don't have get trapped in debt. Don't live beyond your means. Rich people are rich because they know how to live like they're poor. Poor people are poor because they live like they're rich.
Drinking too much alcohol will magnify and compound any of your other problems. Same with drugs.
Don't do anything illegal or unethical or cheat on your wife, your business or others. You can sleep peaceful at night with no regrets.