The good ones don't leave you with something to heal from. The bad ones have left a mark on your emotional/mental state. Healing takes more time.

I've been blessed when it comes to therapists so this is my experience with people in general. Friends, neighbors, coworkers... I've had good ones, bad ones and some that still nag at my emotions and thoughts in a negative way. I try to stay mindful and kick them out of my head when they intrude. Its harder if I'm upset, sad or angry to stay mindful, but I try it anyway since the only thing I have to lose is bad feelings about something from the past.