I recently retired, again, the last 3 months that I worked, I cut my hours down to 30 per week. I trained and helped out where I could, at first I felt like you do, then I said...self, what difference does it make...you are retiring, let it go.
When you strip everything away down to the core, it is just a job, one that someone else will do when you are gone...life goes on!
Relax, this too shall pass.