I think your last sentence is the crucial one. Up until 40, I could pretty much push through whatever tasks I needed to do regardless of how poor my sleep habit

I think your last sentence is the crucial one. Up until 40, I could pretty much push through whatever tasks I needed to do regardless of how poor my sleep habits or diet had been. Now, as I approach 50, I really feel it on days where I haven't been taking proper care of myself.