Fun fact: I am learning greek.
Not so fun fact: I suck at it. Memory fails me constantly, I wish I could have ECC for brain or something :)
My feeling of that mental deficit started showing in other areas: I no longer think I am even remotely good in any of the things in my life. Coding skills are no longer needed, managerial stuff is still extremely hard, and even my english sucks ass.
Probably it just stuff stockpiling on me in general, and the idea that I cannot dream "I'll become good at this some day", because it is hard to afford that line of thoughts past certain age.
Or maybe that's what happens when midlife crisis strucks at 40 and you already own a motorcycle (or two) :D