I've started, when do I finish?
There's no neat answer to any therapy-related question really, including the one I often get asked about when to end therapy. As I don't work with a set number of sessions as some therapy does, an ending isn't defined from the start of our meeting. But in my experience, you'll know when you are ready to end.
It may be that you find yourself experiencing more and more 'successes' outside of the consulting room - 'successes' being measured against your original goals, such as drinking less, flying off the handle less, being kinder to yourself. Perhaps you have a better handle on those parts of you that used to take hold: the angry or jealous or guilty part. It may also be that you feel more resourced on the inside to deal with stresses, even if things don't look too different from the outside. Or, of course you have run out of funds, or your therapist isn't as skilled or supportive or even likeable as you'd hoped and you want to try someone else. As with any relationship, some work, some don't - including the therapy one.
Therapy can also, sometimes, 'get too much' - the talking and reflective thinking will inevitably take us 'into our heads', but some of us may get stuck there, endlessly working out our motivations and those of others around us, so that we can end up losing touch with our feelings entirely. I'd argue that good therapy will do its best to avoid this happening, as it shouldn't ignore our emotional world and the body that it resides in, and thus won't allow 'analysis paralysis' to set in. But for some of us, it may take a while to feel truly comfortable with tuning into our feelings - I certainly did when I started therapy - and this type of therapy may feel too much. It may even be that you need a break to assimilate what you have learned and come back to therapy at a later date - or try a different type of therapy that relies more on the 'head' than others - such as cognitive behavioural therapy (CBT).
Your therapist may disagree with your wish to end - I hope because she, or he, has your best interests in mind. I have often felt some endings have come prematurely - but it's not up to me to insist on anyone coming - the ball is always in your court.