The number one rule is to always trust your coach. He would not allow you to spar if you were not ready. My motto that I preach to my fighters is “TRAIN LIKE YOU FIGHT, FIGHT LIKE YOU TRAIN”. It is vital to remember everything that you have been taught. Sparring is a learning situation, not an ego booster. Sparring builds confidence.
To finally put to use what you have been going over in your training is the best experience. Making contact with your opponent will educate you on your weaknesses and your strengths. Sparring is where technique is perfected.
Being in great shape also gives you confidence in the sparring ring. To cheat yourself of your training will only cause mistakes. Practice does make perfect, this saying is so true for the Boxer.
Never give your opponent too much credit before a sparring match (and of course in an actual fight). You must believe in yourself, and believe in your coach. Listen to what your coach tells you while in the ring. He sees what you do not, he knows you better than you do yourself. Whatever he tells you to do, do it, he will guide you step by step.
If it becomes apparent that your opponent is not as good as you, then work your defense. If you find he is better than, then try to put out more offense. Respect your opponent by giving him a good sparring match.
Anxiety is common with most novice boxers. The more you spar the more comfortable you will become with yourself. Think of sparring as a learning lesson, if you do poorly, then train better and harder in the gym, preparing for the next time and the next.