If I do something which is either physically or mentally taxing for either horse, they get a sugar cube after. By the time they get it, they no longer see it as a reward for what they did right, but it helps ensure they are feeling good about training, not anxious after the hard work. For the same reason, they typically get one sugar cube when I dismount.
We kiss at them to signal a sugar cube. My trainer has been able to use that when beginners have panicked and horses were cantering away with them - not bolting, but responding to the sudden tight clenching with no stopping. Itās kind of useful in that way.
If I had the timing, I would consider clicker training - I think done well it is a very excellent way to make sure your horse knows what itās being praised for.