Turning 40, Passage of Time, and Health

I've heard that turning 40 was a big deal. I didn't really believe it. Every other birthday that I had was relatively uneventful. There were no notable changes in how I felt. This birthday for me was notably different. Literally from the day that I turned 40, parts of my body that never ached before do now. It's not life altering, but it's one of those "why is this hurting, I didn't do anything to strain that part of my body the day before." This really sucks! The other thing that I noticed is the passage of time. I spoke to a colleague of mine that just had this eventful birthday as well. We lamented about how when we were in high school in class, time seemed to stand still. The best way I can describe the passage of time today is akin to a 2x speed on a DVD player. Sunday night comes, and I wonder where Friday night went. Even during the work week, Monday comes and then it is Thursday night. There is one universal that has been the case, though, for me since work life began: late Sunday night to Monday after work are without a doubt the worst 18-24 hours of the week.