Firstly, I don't consider this a shitpost at all. Your thoughts are well expressed and I can totally relate to how you're feeling.

This caught my attention:

I'll do my best to "get over myself" in the next few days.
I'd better!
It's almost Christmas, and people expect you to be happy and in good spirits, and all that rot.

I can't even begin to tell you how many times I've told myself to "get over myself" - usually because of seasonal depression, fewer sunlight hours, cold, holidays which I don't celebrate but rather use as days of remembrance.

You are definitely not alone