When I was a kid and got bullied, my folks would tell me that one of the easiest ways to mitigate people bothering you is to look/act/seem like it would be more trouble than its worth.

Back in grade school this meant outright fighting the dude (this usually works, even if you lose). It still can apply as an adult; people are rarely going to bother a 6'5 stronglifting looking dude even if he'll get locked up, people just don't want that possibility of getting their ass kicked.

With that said, as an adult, that principle is still the same; do the best you can to make yourself unfuckwithable. Stand tall, speak with conviction, work on your confidence, and hey, hit the gym too, it can't hurt.

The fact that the stakes are higher as an adult work in your favor; even bullies (who aren't total psychopaths who don't give a fuck) aren't going to risk their stability and livelihood to fuck with someone who they really think aren't going to take their shit and push back. So be that guy.

With that being said, this isn't an absolute, as some people really don't give a fuck; so the best thing you can do for yourself is to avoid confrontation to begin with if you can avoid it. Stay away from fucked up people to the best of your ability.