Teaching a horse to stay straight on a line, a curve, a circle or around a corner should be ongoing within your daily training. As your horse's trainer you need to be ultra sensitive and aware of any loss of balance, wilful or not, which can lead to crookedness and evasion.
The importance of staying straight and balanced in your own position and looking up through the horse's ears to a focal point of your choice is crucial as a rider. With the help of a coach, get familiar with your own positional faults and set up a system to help eradicate them. You may perhaps need to change your natural focal point, altering your comfortable seat positioning to something that feels less familiar. Use objects around your training area, such as a gate post or a dressage marker, which, as you pass them, will remind you to physically