focused training and experience is the key.
and also listening to better players if the are willing to tell you what went wrong and how you can get better.
learning from games that went bad is also a good thing if the team meets afterwards and talks about it instead of swearing at teammates.
paintballs only seem to hurt in practise cus your adrenaline isnt where it normally is
true. try to compare a day of marshalling (no adrenaline) and a day of tourney paintball (loads of adrenaline - and I love it!!!).