Before my current therapist, my longest therapist was 9 months. In each case, therapy ended because
1) he told me I was in love with him and that we really needed to stop that. I wasn't in love with him and was destroyed by the accusation from the first person I'd tried to be 100% myself with. It was hugely traumatizing. I never went back.
2) he moved
3) she was being friendly and listening, but we were making no real progress.
4) he was determined that my root problem was perfectionism. No matter what I said, he wouldn't change his mind. I left because he thought he was all-knowing.
5) he was a grad student, and the program had a policy that he couldn't keep meeting with a suicidal client.
6) he worked in the hospital, so we couldn't keep meeting after I left.
7) I had to meet with her to be in a wonderful DBT program. She was nice but wasn't really helping, plus I moved, so I stopped meeting with her.
8) she never really got me. Our first session left me in tears. I kept saying, "Maybe if she gets to know me better, she'll be able to help." After four months, she hadn't realized I'd gotten severely (suicidally) depressed and also had me almost divorcing my husband. My husband wisely told me to stop meeting with her, so I did.
9) after almost every session, I sobbed in my car for over a half hour. At first I told myself I was processing things, but my husband said, "You are MISERABLE. Better that you got no therapy than kept meeting with her."
10) after 1.5 years of working together, I moved.
11) after a few months of working together, he revealed that he thought I was manipulative and basically a bad person. I never went back.
I started commuting the 2.5 hours to meet with therapist #10 and am still doing so.