Consider the possibility that the manic-depression was coincidental. When people have mental things happen for fundamentally biochemical reasons, they often misattribute them to the most plausible seeming non-biochemical cause they can think of.

I have. It definitely isn't. It may have been exacerbated by biochemical causes, but it wasn't caused by them alone. (Sertraline did help me, just never as much as nullifying an existential problem.)

You then tried to substitute a different definition in its place - an alternative notion of personal identity, which might not carry across a sleep/wake cycle.

So you accept the argument?

This alternate notion of identity is not the thing you care about. A small philosophically-minded portion of your brain has decided that it is what you care about, and is now in conflict with the other parts of your brain which don't accept the altered values. Listen to them; while those brain-parts aren't good at explaining things, they have knowledge and in this case they are right.

I have no idea what you are trying to say, beyond "listen to your instincts because are more suited for the real world than your intellect."