You could have someone tell you up down up down up down to the right best. Do this for a week or two and your body will begin to naturally do it correctly.
Try to practise your posting diagonal. You can do this by staying on a circle, go into sitting trot and close your eyes for a few seconds, when you close your eyes go into rising trot then look down at the horses shoulder to see if you are on the correct diagonal. It will take practise but this will teach you to feel the correct diagonal without needed to look.
It's okay to glance down at your horse's shoulder but only for a second or two. :)
When I was learning we had a rhyme: rise and fall with the leg on the outside wall. The other thing would be to trot on a circle and when you are on the wrong diagonal, it will help you to feel the imbalance a bit more.