The nervous feelings lead to rapid ejaculation. He then has another experience which he believes is negative. At the next sexual encounter, he recalls the most recent negative experience and so reinforces the cycle. This may lead men to dread the experience and lose touch with the pleasure of sexual interactions. These are mistaken ideas that lead away from enjoyable sex.
Life is filled with so many arenas in which evaluation of one's performance makes sense.
Taking that attitude into sex doesn't make sense and it doesn't work. Several changes in attitudes can do a lot to help a man last longer. Greater control over timing comes from being very aware of one's body, not less aware. Over the years, men have tried to delay orgasm by thinking about taking out the trash or trying to remember baseball scores. This approach puts a man at greater distance from his sexual experience and therefore lessens his ability to last longer.