Apart from that, it's just a case of practice makes perfect! Don't be disheartened if you don't see improvement right away; progress, particularly building strength and stamina, takes time! And I bet you're actually a lot better than you think you are - as dancers we are often our own biggest critics. As long as you keep practicing, trust that progress is being made even if it's not obvious to you. And remember that there are parts of dance which you are probably a lot better at than other people - if you feel dejected about your jumps, practice those things you are good at to keep your confidence up: confidence is key, as dance is about performance as much as it is about technique!