what qualities should personal trainer have?

I prefer combinations of all of the above, lol. I want someone who is friendly but committed to urging me to do more than I think I can. The trouble is, I also want someone who will recognize when I say "I cannot do that" it isn't that I don't want to or don't like it. It is that I am telling you a physical "I cannot do that" issue. That's where I trip up. I've left 2 trainers so far over that issue. 2 shoulder surgeries and 1 knee surgery and there are just some things I can no longer do without protracted pain afterward. It isn't worth the fight to me. Now I do my own thing. Takes me longer to get to the end result I'm sure but I'm more comfortable on my journey.