Guess I can chime in here
😀 In my 4th decade and feel great! A huge difference from undergrad, but here are my observations:
1) Yes, I could still hang with the young'uns, but maybe not til 2am at the pub
😀 I would start strong and when it was time to go home and take my Metamucil, I would slip out and go get my beauty rest.

2) Physically, I am in very good shape and actually had an easy time with farm practicals, walking miles to/from class, basic stamina, etc.
3) Studied much more effectively since cramming and all-nighters are not an option. Many of my young classmates would party hard during the semester and put off projects until the last minute and stay up all night. Nope, not this old fogey. In UG I did the same thing, but in vet school I planned way ahead and actually got things done early.
4) Time management - seems much easier this time around. What used to seem overwhelming is no longer after years of corporate stress.
5) Getting along with the young'uns... No problem at all. I think they appreciated me because I don't act old and can hang. Not having to go home to a family, I was usually the first to recommend hitting the pub after a long afternoon in the dissection room.
6) Staying active - exercise is a must! I played on the vet school's soccer team and actually surprised some of the 18 and 19 year olds. Of course, I couldn't walk the next day
🙄
7) Like Squirrelsrule said - your life experience will help you more than you can even imagine at this point. It's weird, but everything is just easier and makes more sense. I attribute a lot of this to familiarity.
It's really all about your attitude and how you approach it. I found that they are initially intimidated by us 'old fogeys', but once you start to work together and integrate, it's like there is no age difference (except when they chatter during the entire lecture, talk about who they shagged the night before, came in wearing the same outfit as the night before, etc

dang kids ). We are typically seen as stable, dependable and leaders. I loved my 'young'uns'. I found it easy to become protective of some of them because you see them having typical 20yr old issues and you just want to give them advice and a big hug.
You'll be fine Bisbee! Just go with the flow.