Its natural brother… you know why your tense ? I’ll tell you why . the guy across the ring want to cave your head in. LOL here is what you do . before the bell ring you have to fool yourself a little bit, take a deep breath, let it out slowly take another breath let it out slowly, relax all you muscles and don’t think about anything other then going out there and having some fun. . The more you spar the easier it will be to get relaxed.