the best way is just to spar and the fear disappears. i used to spar at kickboxing and the guy i sparred with just went full out and i got proper beaten sometimes. as you can imagine i didnt enjoy it most times. but now atTKD its more controlled and i learn more. ive now lost almost all my fear that i had and i enjoy it now. moral of the story, start with light sparring, some thing you can enjoy and work upwards.