"Lateral flexion" is often misunderstood. Many riders bend the neck instead of getting flexion at the poll (joint between C1 & skull). Flexion turns the forehead slightly, without requiring body bend. However, correct bend from nose to tail always includes poll flexion. Learn how to do it here!
Make sure you understand the difference between energy and stored energy - it is the difference between speed and impulsion.
We want our horses to be confident to step up into our rein connection, yet not try to push through it.
Think of riding your horse’s outside hind leg actively through the turns to your jumps, to keep that canter well engaged behind. The outside hind leg is the beginning of each canter stride. Engage that hind leg, and you will engage the entire hindquarters.
The fastest cross-country horses are not necessarily the fastest horses in general, but the ones that are the easiest to set up for the jumps. So work on your horse's adjustability.