For me i have noticed a few things.....being middle aged It takes alot longer to build muscle at the gym, but you can still get pretty strong with the muscle you still have, but where it would take a young guy to build muscle over 3 months it might take a year for me. Next is stress in general, where these days things dont really impact me as much due to experiance when things impact me they impact me alot more, if that makes sense, meaning axiety hammers me more which i have to think around to over come... So in addition to the stress thing, i put on weight easy and it seems harder to take off. Maybe i aint burning energy as efficently. Also the value of the family is alot stronger, meaning family is everything with kids etc. Managing kids issues gives you an outlook on life where theres more to life then just work in the office i'll add one more, dealing with death in my related family, i have had to deal direct with organising funerals etc, going through the aftermath, clearing out peoples stuff they leave behind after they pass away. It gives you another outlook that you dont experiance in your early years where there is always someone else to look after these things.