As far as musically, has your playing gone stagnant? Do you openly and purposely challenge yourself? I did a quick read on the journal that you had linked. Other than the co-worker, I think everyone struggles through a stage somewhat like what you go through. Mine was when my father died, rather unexpectedly, during a routine surgery. It made me realize just how truly short life is. And really, only concern yourself which matters most. I can not tell you what that is, as it can be different for each individual. I am not a professional musician. I saw sheet music (in 1990), but I always challenge myself. I may fail a million times on a piece of music. When I get it done though, it is a very (and truly) happy moment.