Fear is a subject that a lot of fighters don't like to talk about. They want to stay positive, focus on the win, and don't even want a split second of a thought of fear to enter into their mind. But the fact is that all the fighters do have a certain level of nerves and fear going into battle.
GSP has probably made the best contribution to this field in terms of admitting that he is scared of a lot of things going into the cage, but when he walks to the Octagon he uses his body to mimic what a supremely confident person would look like and that turns his mind into believing it.
One of the best things that fighters can learn in this subject is Randy Couture's approach. He talked about making friends with the worst outcome and realizing that even if he did lose a fight, it's really not that big of a deal. His friends and fmaily will love him, he'll wake up tomorrow and sun will be out, and live marches forward.
Also, another thing that a lot of fighters mention on the subject of fear is that it's a good thing. It keeps them sharp and some fighters even feel if they weren't scared that would be bad; they wouldn't have a competitive edge.
So fear is natural and when it comes to fear, there is nothing to be afraid of.
Quotes on Fear from MMA fighters
Georges St-Pierre quotes