When u try to perfect the word r  impress someone r lack of training and rehearsal usually lead to this problem. At the end u become excessively aware of the environment leads to 1. Pounding of heart 2.shortness of breath 3. Light dizziness and headaches 4. Dryness in the mouth 5.shaking of hands and legs. All these things gets added up by ur sympathetic and parasympathatic nervous system. Leading to further more problems..