I found talking to the horse helped me alot. However it's been a long time since i've ever felt nervous on the horse. If you can ride with someone else every now and then can help too. Especially if they have a confident horse and are confident themselves. You could try smaller rides to help boost your confidence, areas your horse is familiar with.
Whisks used to be bad for stopping and trying to turn and go home then not moving forward, I used to keep her going in a tight circle. She soon figured out it was less hassle to keep going. [or either that she probs got a bit dizzy and didn't know which way we were going lol]