Have you accomplished all your goals in therapy? If not, I think that is a good reason to stay. Or are you thinking of quitting because you don't seem to be making progress toward your goals? Or the progress is too slow for you? I think the reason you want to quit will help determine the answer to your question.

I did quit therapy with my first therapist and it was absolutely the right decision (even though I didn't really make a decision--I just kind of accidentally quit). We had ceased to make progress--I was completely stuck. When I asked her for ideas on how to get unstuck, she said I could keep coming to see her and we would do more of the same (fairly shallow talk therapy). I think when I realized she had nothing more to offer me and that continuing to see her would not help me get unstuck, I became able to quit. Later I found a therapist who had a larger skill set and could help me.

I don't know if that is similar at all to what you are facing. Can you say more about why you are considering quitting therapy?