I rode a QH for 2 hours, we spent most of it trotting, or fighting to trot, and when I let her go when she wished, we cantered/hand galloped 6 or 7 times. She sweated herself soaking wet (which I know is more due to her fighting me at the first part of the trail than actual working, she is very high energy), but she wasn't tired or even blowing hard until the very end of the ride. I know her owner likes to gallop her in open fields, so I am sure she was conditioned for it to an extent. It was astonishing to ride a horse that could gallop across several acres, slow down to a spunky trot, whip around, gallop back across those acres, come to a stop, and not even blow. I was worn out way before she was.
Think of it not as a failure but as a success in how not to do it.
Don't look in a horses mouth for a gift.