If everybody who said "no more, thank you" was called a quitter, no bad or painful thing would ever be stopped. You have the absolute right, as a free and self-governing individual, to end whatever you're doing with anyone: work, study, social life, or therapy. In fact, you may very well have the obligation to say "stop" if anything is causing you pain or is entirely against your values, as decided by you and by no one else. If there is no way you can perceive that your last three sessions will be of value to you, there is no reason at all not to stop now. It's YOUR perceptions that matter.

If you want to go the whole hog and be fair to T, you might want to consider emailing him/her, telling him/her your own feelings, and giving him/her an opportunity to state their own views. Of course, you may very well have done this already. In which case, the issue is moot. You don't have to ask anyone's permission to terminate therapy. If you feel it's right, after seriously thinking about the matter, then go for it. You won't be doing anything wrong in any sense. Take care!