Well first off relax...you'll tire yourself out more if you are tense. Sparring is supposed to be a workout and it's also supposed to benefit both fighters so if the 34 year old is trying to knock you out, just don't spar with him! Another thing you might want to do is visualize boxing who you spar when you hit the heavybag...this way you trick your mind into feeling the flow of sparring so you go spar later and you feel more at ease.

You're only 14 don't get worried about getting hit or hitting someone, it'll come...I mean you throw enough punches you're bound to land something....and getting hit is just a part of boxing it happens