WADR, that's nuts.I've fought a lot of "up and comers", and with my luck I'd put him down. I'm just as strong as I've ever been, though not as quick, but what I've lost in speed I make up for in experience and guile. To some degree, everyone telegraphs what they're about to do, and the more cocky and overconfident they are (that almost always goes along with how many expectations people have in them) the worse it is. When you get in on someone and counter effectively, it can go south for them really fast.
Not meaning to brag, but I did beat (on points in a 3/3) someone who was the #3 or 4 contender, depending on which organization you ask, not that long ago. He was a great puncher, my forearms hurt for days, but his defense was poor.
Hmm. You still have a lot of fight in you. Each brain is different. There are some fighters who don't sound punch drunk at all and are very sharp still, other fighters who have much shorter careers that are demented before they turn 40. Are you waiting to feel old? Your brain and body could have complete different levels of health which is what you seem to be struggling with. It doesn't matter that at 43 you can hang with up and comers, it matters that for however long you have been boxing, you have been receiving blows to your head.