Signs You're Getting Old

It must be a sign that I'm getting old when I actually prefer Mondays to Fridays. Used to be, Friday was my favorite day. Usually the weekend would start on Thursday with Happy Hour and then on Friday it was out directly after work until all hours, Mondays were to be dreaded. Nowadays, by Friday I'm tired and running down on energy, yet Mondays are fun! I'm well-rested, re-invigorated with energy and enthusiasm for the work at hand. I always seem to get a lot done on a Monday and the day just flies by. Preferring a Monday to Friday ... what's up with that?