Thank you! And the horse sold shortly after I fell off. But I did get back on (due to my instructor)
You should start with the same horse because you may just freak when you get the stronger horse, if you work with just ground and raised poles you will gain a stronger sense of confidence
Training with a nice and calm horse can be a good idea. Anyway start small and easy at a height that you feel confident at. Then go higher and when you feel confident at that height raise the jump again.
Good luck I am sure it will ne ok soon!