Horses are naturally inclined to move into pressure. In your groundwork you will have worked on teaching your horse to move away from pressure. That’s why I find it hard to see so many horses leaning into reins and against legs when riding. On the ground you would fix it, where as in the saddle you let them get away with it.
I would like my horse to know he can release pressure all by himself. I apply pressure (either with my seat, leg or reins), keep applying until the horse does what I want, then release. The horse will not learn from the pressure but from the moment of release. He will look for this.
I put both legs on (pressure), I wait till the horse walks forward, take leg pressure away (release).
I put my right leg on (pressure), I wait till the horse steps to the left, take away my right leg.
I hold both reins lightly (pressure), I wait till the horse gives to the rein, the pressure is released.
Quick side note: two legs on, you are working on your horse's whole body. One leg on, you are working on direction or shape.
A good way to teach your horse to move away from leg pressure is to ride without reins. This way you can concentrate on one cue, move away from my leg.
Learn to ride without reins in a following post.