a few months short of turning 30 and i really don't feel old at all, most likely thanks to skating. i try and skate as much as i can, which - thankfully - is several times a week, but i also know my limits and when to take a day off, for instance if i've really been skating so much that my body lets me know it's too tired to interact with a skateboard that day i won't waste my time forcing things. that way i can foresee & avoid 'bad' skate days, and consequently save my energy for when i'm in better physical position. i think managing your effort is key, as well as listening to your body in general, something modern society is quick to distract you from, and consists in giving yourself enough rest but also watching what you put inside yourself. some recreational abuse is fine, but always make some time to check in on what your carcass is telling you before you really cross the line of what is reasonable depending on your life goals (i find remaining physically able to keep skating to be a good one - works for me at least, and regularly keeps me in check). also it's fundamental to hydrate yourself more than you think you would, and eat good food (look shit up, cook accordingly, experiment).
i find a lot of that age thing to be mostly in your head. my skating kind of took a dump when i was around 25, 26 because i lacked hindsight & was making closing in on the number 30 quite a big deal to myself, that and - most importantly - i was almost exclusively skating with friends who were older around that time, and they had entangled themselves in short sight & close horizons, making it clear they had given up on learning new shit (or even some of their old tricks again), in favor of constantly raving over the good old days, back when they had acceptable backside flips or whatever. truthfully a few of them had never been that good in the first place, and there's nothing wrong with that at all, but that along the endless ramblings and tales of old spots they barely ever really skated anyway would make them come off as confused, disenchanted young adults with personal difficulties embracing their own growth, rather than genuinely motivated skate rats with a spark.
constantly being in the vicinity of guys in such a mood would make me feel my own age so bad. i started giving up on a lot of my old tricks just because they would stop working, maybe as a side effect of my brain 'adapting' to a fictional condition. i still skated most every day and learned stuff, but i'd really just be messing around with nollie tailslides and step hops the whole time (i still love them). then 2 years ago i had to move back to my hometown which is really small, but always had a great local skate scene, and i ended up skating with younger kids again, which even felt weird at first. turned out they had so much energy, and it was so communicative, we all started to fuel one another's fires. i started doing a lot more flip and ledge tricks again and not only did i relearn most everything i used to be able to do all the time, i also learned tons of new shit i had never thought i would have been really able to do, even as a kid - i even ended up learning some of my 'dream tricks', basic stuff i'd grown up seeing & loving in mags, that had never clicked for me before as a youngster. kids are competitive - they will try and learn just about anything, check in on what you're doing, learn your shit - sometimes before you actually do, then you're the one learning their shit. they benefit a lot from the perspective of skating with older guys (i.e. they get ideas, study postures, apply advice), and older guys can easily benefit from the effervescence, and also occasionally be put in 'defense mode' when you see an insecure kid really trying to bite your shit and you want to show them how (you think) it's done...
that 'getting old' mindset really is a downward spiral one might consider getting out of before they actually get old, as long as they have some passion left, and some spare time (even if scarce). the way i think is along the lines of, life is short and fragile enough as it is, fuck it being too short for one not to ever skateboard the way they always wanted to skateboard, experience the feel of the tricks they've always wanted to feel (albeit that will take the corresponding amount of work). try to remember the 12-something-years-old version of yourself going through their first few set-ups and generally just first finding out about skating, then try to become that kid's favorite (or dream) skateboarder... skateboarding & character goes hand in hand. treat yourself accordingly and age (especially in your thirties which is still young as fuck in the grand scheme of things) shouldn't hold you back. every night i go to sleep feeling like i've never skated as well as today before and i'll skate even better tomorrow (whether i realize it on the spot or not) and i'm so thankful to have that priviledge. experimenting with the limits of what you think you can do, and what you can actually do is a virtuous cycle which to me feels rad as fuck !