I've succesfully gone through the stages of grief around my current job and have moved on to active job hunting. The way my brain works, is that I am now legitimately spending every fleeting moment and thought on the problem of what I want my next step to be. Reaching out to friends / ex-colleagues / work acquaintances and thinking out loud helps a lot, but it also spurs more thinking and reflecting and pondering.
Meanwhile, I've lost any and all motivation to work. I knew I need that inner motivation to work, but I didn't know I needed it this much. I now realise I've been lucky for always having had some kind of motivation for the past decade, so it is jarring to have absolutely none of it and to feel so adrift. Fortunately I really don't have a lot on my plate at work. I can just do a bit of quiet quitting and I doubt anybody will notice or care. Especially since my conversation with HR last week went like "yeah, you're one of our high performers, so we get it if you want to leave. We'd love to keep you ofc but it's best if you just take your time to figure things out".