I've never had depression or anything as serious, but I definitely know what it's like to feel burned-out. Twice I've had the feeling of just not wanting to do

I've never had depression or anything as serious, but I definitely know what it's like to feel burned-out. Twice I've had the feeling of just not wanting to do anything: first towards the end of my PhD, and then after a ten-year run in the finance industry. I had pushed so hard for so long that the end results were irrelevant. If you're in therapy, start with why do you feel the way you do. Also, what do you actually want to be passionate about? I've found that working on my goals has been my biggest source of happiness. I also seek-out other people who are interested in similar goals, which has led to a lot of important social connections. My conclusion is that living in the present and not worrying too much about the past or future has been the most critical aspect of happiness overall. I think you might benefit from practicing that as well.