I get this feeling every so often. It goes along with hopelessness - feeling like what I'm doing isn't going to make a difference and I will never feel fully happy.
Two things help me get through this. First - rest is allowed. Dying is pain and stress and then nothingness, it's not rest. What do you want to rest from? You are allowed to take breaks from therapy or work or any activity or goal. Is sleep and relaxing enough or does that not actually feel restful? If so, what can help you sleep better?
Second - wanting nothing is scary, depressing and makes it really hard to do things. If you were not in pain, what would you spend time on? Is there a particular food that you want to try, a place you want to visit, a movie or tv show you used to be interested in? I find myself so focussed and overwhelmed by pain that I don't do anything that's fun and interesting to me. Put your attention on small pleasant things like a hot drink on a cool day, interacting with nature, trying to find something that feels ok and takes off some of the pressure. Sometimes I start a journal with the phrase "I want..." and ramble about what I wish could happen.
For me, I usually feel like everything feels just as shitty now as it used to, esp because things go up and down and the down days are still awful. I try to focus on short-term things because I know I can feel better in an hr if I (for example) listen to music now, and it doesn't matter whether tomorrow will be better or worse than today. Things go up and down and our brains fixate on the downs more than the ups. It's helpful for me to be more aware that I can feel good and bad things at the same time because it's something to aim for that's more realistic and achievable than feeling overly positive, hopeful and optimistic.
In all these areas, support from other people really helps. Do you have friends/family/colleagues or professionals that can take some of the burdens off? Can you find people to help you focus on one day at a time and supporting you to do nice things for yourself?