I am sorry you are feeling so terrible. And that is so sad about your cat.

For me personally, keeping a little bit of a schedule helps, such as making sure I eat meals, shower, sleep, work or do an activity.

Also, it is very tempting but I find not socially isolating helps. Isolation can cause me to spiral. If you are lacking a support network it might still be helpful to get out and volunteer or something to put you in contact with people. Or even an in person support group? I also wonder if you might benefit from being around animals since you lost yours, perhaps volunteering at a shelter? Or would it too hard emotionally?

If you get seasonal depression, maybe see if you can prevent that with a light therapy lamp after discussing with your doctor (think this can give some people hypo/mania). Or some walks outside?

Self compassion during these times is important. Try doing things that make you feel good--treat yourself a little. You deserve it. Self compassion meditation helps me sometimes.

Okay, this is a lot of rambling, and you probably know a lot of these things haha. I really hope this doesn't last long for you. Also, is there something about the remeron that you don't like?

Hang in there.