I have burned out at least 10 times in my career. The last time, it was like I lost half a decade, even though it didn't last quite that long. It was as if I had amnesia. I fell into a deep depression. I considered killing myself just because everything seemed so difficult and pointless.

Give yourself some more time. You might not emerge exactly as who you remember, but its possible to mostly recover from the pretty extreme cognitive impairment that you are likely struggling through.