I know how that goes, I still run, work out, bike ect. Nothing will tell you just how old you are like playing city league basketball at 40 against kids that graduated from the local college and played sports there, they hand you your @$$, then have your knees and ankles hurt for the next 6mo, it will leave you asking yourself. Why the hell do I put myself through this every year. Answer is to stay 1 step ahead of your own kids for as long as you can just so you can keep pace with em for a few more years, it's worth the memories made when you set up camp in places few want to go. Then still have enough left in the tank to shadow a heard till they bed for midday, then make your stalk. I have 1 girl that's only a year older than yours, I bet you know exactly what I mean for the memories, I have another girl that's 3 so I'm gonna have to keep it up for a while yet.
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.