I know what you are talking about...except that I never had the problem in practice. After a NH  

 at my first meet, I got 10' at the next one that I went to. After that it seemed like I kept getting 9'6" over and over again. Believe me, I was frustrated. At the last meet, I got 10' again. The only adjustment that I made was a mental adjustment. I was worried so much about making 10' that I would overthink the entire jump and miss. At the last meet, I visualized the jump before I went, then cleared my mind, took a deep breath, and vaulted. Basically, just let your body vault and forget about the crossbar being up there. When I cleared my mind and relaxed my vault totally changed...it had better form, was fluid, and it felt easy! You might be overthinking the vault and the height, and your frustration might just be adding to your stress. Try to relax and you will both enjoy and improve your vault. 
