I'm 63, been riding for about two months. I've primarily been focused on distance and average speed when doing my rides. Quite often have the wind on my nose on the final leg home (north wind) and the last mile or two am totally gassed. Find the wind demoralizing - at least a hill ends.... Usually a 15 - 20 mile ride. Average speed has been steadily increasing and can do 25 miles in the morning and get thru the day without any negative side effects from the ride. Sometimes a power nap, but what's new about that? I've been taking it easy the first 2-3 miles, then pushing as hard as I can.
An interesting thing happened yesterday. Did the usual warmup, then focused on cadence and being in the proper gear instead of pushing. Let my legs do it instead of making them do it. Found I had been mentally and visually anticipating upcoming hills instead of listening to my legs. Didn't push quite as hard on the flats and downhills, throttled back to about 80% on the hills (probably a slight rise in the road to most of you) and boy oh boy was I surprised to see I had done my 15 mile loop .7 mph faster than ever and wasn't close to being gassed on the way up the "hill" I live on. (It is a hill, get 30mph coasting down it at the start)
Quite a revelation to me, as I haven't read any training material, nor do I have any experienced buddies to hang with ('cept you-all!) Now am looking at a 30 mile ride without any fear. Yup, good stretches before and especially after. Lost 12 lbs, am on the high fat low carb diet that I discovered here and feeling great!
I'm a musician, and kind of relate this to letting the music come thru you rather than making it happen. Just kind of stop thinking and let it happen.