I started riding at 50, and only started cantering at 53 - last October. Now I love doing it, but I had a HUGE mental block. In my defense, I had an injury after 6 months of riding that will probably leave me with a sore hip forever.
I'm not trying to pee in anyone's Wheaties, but you might try cantering with a western or Australian saddle. I recommend one with a horn. Grabbing the horn while cantering is counter-productive to a good canter, but it IS nice knowing the option is there.
I also was trotting with very long stirrups, and found the setting that works best for me trotting makes it hard for me to keep my stirrups at a canter on my Appy.
The nice thing about an Australian saddle with a horn (if you can borrow one) is that the saddle retains an English feel, but the poleys and horn give one the feeling that he can do anything and stay on. I know I cantered and galloped during my few rides when I was 20, and had no fear. But at 50, and with an injury, I've found fear makes me tense, tension throws me off-balance, and a vicious circle kills my progress.
This week was my first time cantering in my Bates close contact. It felt about 90% the same as cantering in my Aussie-style saddle...but I would have had a VERY hard time learning if I started it in my Bates!
OTOH, my daughter-in-law (25) had her first ride in an English saddle today - the Bates. After a couple of minutes, she asked our little mustang for a canter and then laughed her way thru a few laps! You see, I'd LOVE to be a young punk - say, 32! - and learning to ride.
Oh - and if borrowing an Australian saddle isn't an option, a western one isn't bad to learn cantering on. I used both western and English today, and the western is maybe 70% similar - enough to practice on, get the basic motion, and then go back to English. I personally find switching tack and riding styles to be like cross-training in a sport.
I probably shouldn't post this picture, but this is Trooper & I about half a lap into my first attempt at cantering, and his first attempt at cantering in a year (and maybe third in 4 years). It looks more like I was flying in formation with him - loose formation - but maybe you can see why I didn't feel good about trying it in my Bates
. In my defense, 3 months later we both love cantering - so much so that I have to work to convince him not to canter any time I sneeze