ATAT-Sorry this one didn't work out. Will you be looking for another at this point? Do you have a 2nd therapist now?
I've told this therapist I was quitting a number of times. I think I emailed him to give him a heads up that the next session would be our last. Another time I sent him a long email, to which he replied kindly and with caring; so I decided to go back. When I was really hurt, I've thought about never showing up again. I wasn't contemplating that with a goal to be mean or spiteful; rather it was to protect myself from harm at a time when I was already extremely hurt and vulnerable. Things are better now, and I am still with him. I feel like I committed a long time ago--committed to make it work with him, if that makes sense. Sometimes I've felt more committed than he was. So here I am, still with him.
I had a last session with the one prior to this one. We had a good ending. But we knew a few months in advance.
With the ones prior to that, I can't remember exactly how I ended the therapy. But I didn't have attachments to any of them and no abrupt need to end, so I likely told them in advance or at our last session. I remember telling the one a few weeks prior to quitting that I was on the fence. There was one a few years back who was really shaming and who seemed to have more emotional problems than I did, but I don't remember how I quit with her. She also cancelled a lot, sometimes with less than an hour's notice, which really pissed me off. Especially because she actually charged me for a missed session when I had to cancel due to handling a serious family emergency. I never paid.
It's so difficult to find a good one. Every time I thought seriously about quitting, I remember my experiences with exploring others out there, in addition to those I've worked with in the past, and I know I wouldn't find a higher quality therapist unless it was sheer luck. When I weigh the pros and cons, the scale always tips in a positive direction.
The most important consideration, in my view, is what makes things most tolerable for the client. At least what I've gleaned from the literature, it seems that therapists are used to clients leaving abruptly, or clients leaving then coming back. And since you haven't been working together for very long, email seems a reasonable approach. Leaving empowered sounds a whole lot better than leaving feeling disempowered, which might be an influential decision-making point for anyone trying to decide how best to quit.
I hope you are still ok with ending with this one ATAT. Decision remorse can really bite.

Hopefully it will work out for the best.