I don't know how to know for sure what is causing your lose of interest in therapy. But for me, when I was in panic, chaos mode, therapy was the only thing that helped me hang on. Everything that happened there seemed very important.(and it was)... but now I am not as distraught as I was before, it seems like therapy is less important. But truthfully, I am just now getting to the place to understand the causes of the distraught, panic and chaos...and it is harder work because its about talking about hard stuff, changing thinking, changing behavior and its not fun... so there are times it feels like I've lost interest. As far as it being a symptom of depression, have you lost interest in other things that are important to you in RL as well?