Tishie, no matter who we are, or how patient or understanding we are, or how smart and empathic we are, we all have our limits. here is going to be someone out there who punches your combination of buttons and you need to know when you need to back off and just let someone else be that person's ear and shoulder. I have had to back up hard on a couple of people because if I don't things might get said. Why? because those special buttons get punched, and in spite of my hard talk and seeming intolerance, I don't want to add to their pproblems by blowing up. If I do, then what I would say would not be retractable, ever.
There are times when realizing that you have the limits is the best and kindest for both parties. Yeah, it's nice to feel like you can understand everything and everyone and be there for everybody, but you know, this is right where most professional therapists make their biggest mistakes, the ones we all get warned about in school. Know your limits and know when you need to say "I can't handle this person or this situation right now, or maybe even ever". One professor told a student who insisted that we should be able to handle everyone that she was developing a "God complex".
There is no shame knowing that your limit is hit. It's OK to say, "Not now, OK? I just need to deal with something else right now. Thanks." I have to avoid the sister-in-law, which is not easy, but it's essentially the same deal. Good luck, hon.