How Do You Not Take On Other's "stuff".

I read a lot here about people s feeling, thoughts, issues, etc are theirs or about them and not yours or about you. But what someone says or thinks or feels, feels directed at me (regardless if it is or not) it is very hard to allow their stuff be their stuff and not bring it into being my stuff and not allow it to affect me. I completely get the concept but I am having a very hard time doing it. Like when someone says "don t take it personal", it s hard not to when it feels personal.... How Do You Not Take On Other s "stuff".
https://www.myptsd.com/c/threads/how-do-you-not-take-on-others-stuff.66931/