I can totally sympathize with you! I worry about everything all the time, to the point that it causes stress headaches & dizziness. What I tell myself is that worrying about it constantly won't get you very far, but hard work will. Focus on the skills you need to get and give every practice your all. Realize your weaknesses and work on them at home. I don't mean actual skills, but strength and flexibility. Talk to your coaches to see if they're willing to give you conditioning at home tailored to your weaknesses.
And most importantly, whether you think you can or you think you can't, you're right (Henry Ford). If you go into each practice defeated and telling yourself that you won't get your skills in time, you won't. Focus on the positives and work hard. Tell yourself that you can do it, and when the conditioning gets hard and you want to stop, just remember how badly you want to accomplish your goals and use that as motivation.
The only thing you can do is work hard and keep a positive attitude.
