Depends really, on the type of therapy the client seeks out... so what happens in session varies from client to client.
I'm primarily there because I need to learn emotional regulation, so my main goal for therapy is to learn techniques that will help me in my relationship, and thus in life. But sometimes session doesn't go as planned, sometimes I unexpectedly spill the beans on things I didn't even realize had bugged me during the past week
I was very rigid going into therapy, I just wanted it to be about "The Goal", but in becoming more comfortable with my T, and attempting to be more flexable, I've actually started talking about some of my currently shytti experiences, and I'm finding therapy pretty therapeutic. Who woulda thought??? Definitly not me no
I'm really not the dredge up my past traumas type of gal, (although there are many and I'm far from a closed book) but I am open to talking about it when its relative, like if its actively affecting my present.
So at the moment my therapy is fluid, we discuss and work on whatever the hell I'm struggling with presently, but it always ends with a type of goal or focus, so as not to lose track of what actually brought me there.
Its been a really validating experience, I never would've imagined it being so, that's for damn sure.