When do you let it go vs speak up? Need help developing tough skin.

I’ve been in HVAC since I was 18. I’m 21F now, and the only woman on my team. I usually just keep my head down and avoid conflict, but lately I’ve been wondering if I’m shooting myself in the leg by not speaking up when things cross a line.

I’m pretty good with my team minus one guy who has had a one-sided issue with me since I started. For example, a couple weeks ago, he yelled at me in front of a customer, completely unprovoked (I did nothing wrong). I didn’t say anything, I just totally shut down (I always shut down when someone raises their voice lol) and kept working…I really don’t want to be seen as dramatic or hard to work with. I have mentioned his behavior a couple times to my boss when I initially started my current role, but all I kinda got was “that’s just how he is” 🤷‍♀️ and I dropped it.

But now I keep thinking: Am I just making it easier for people to treat me like shit? I’m super kind and outgoing when it comes to my coworkers in general. I think they mistake this for weakness often. That being said I really don’t want to start any problems, or get anyone involved like HR and stuff. I’m doing my best staying out of the way from this particular coworker as well.

Would love to hear how you all handle this kind of stuff. I’m still working on developing tough skin and not taking shit personally. Thank you!😊