Feeling Numb After Mania: How to Get Back in Touch with Myself?

Sounds like extremely high stress causing dissociation symptoms. Mania can drain you physically and emotionally. I think it's been making you sick, like too much caffiene would. It sounds like it's ramped up from normal depression to burnout depression. While it's happening, focus on recouperation. Naps, water, sitting in nature, alone time, minimal electronics. Pet your dog if you have one, cancel responsibilities for a few days. You have to make sure your recouperation can keep up with your depletion. That's extremely important, or the problem will just get worse. In the long term, try to prevent this somehow. The root is going to be the manic episodes, and lifestyle stress. Any way you can find to lessen the impact of these things, will help lessen the consequences afterward. If you can find more positive, less-intense outlets for mania, or find a medication that works for you, or find better accomodations for manic episodes from the people around you, that would be good. Avoid delegating important tasks to yourself to do specifically when you're manic. Manic phases can be powerful, but that power is chaotic, and trying to harness and control it will add unnessiary stress. And lifestyle, try to identify and change the things around you that are having a negative or intense role in your life. If people traumadump on you, establish boundaries. If there's yelling or loud music in the place, ask for less of it. If you cook, delegate to others and order food sometimes. If you have weekly social gatherings,go every other week. That kind of thing. Start metaphorically unchaining yourself to the stuff in your life. Make sure you expect a reasonable balance of supporting vs being supported. I know it's easier said than done, but this is the stuff that helps.

That sounds similar to what we experience when we depersonalize/derealize. Ice and/or cold short showers helps. As well as naps, but those aren't always an option.