Whether it be the permanent effects of age, the lack of stimulation from graduating from school and observing waning fluency or external factors: do you feel less keen/sharp? Does it bother you in any way?
Personally, after being on night shift recently I noticed much of what I was an expert in has since diminished—though this is temporary. I have regained my capability for critical thinking since then. But I still see the expected fading of well-versed knowledge of which I learned in academia. It makes me feel like I wasted some time there. Although normal, it does bother me because I highly value being well-versed in a diverse array of topics.
What about you?