I am not sure I understand your question so I will answer it in two ways.
During sex why do boys/men ejaculate prematurely?
Premature ejaculation is when ejaculation occurs before the person wishes it. Most cases of premature ejaculation do not have a clear cause. With sexual experience and age, men often learn to delay orgasm. Premature ejaculation may occur with a new partner. It may happen only in certain sexual situations or if it has been a long time since the last ejaculation.
Why do boys/men loose control when they are excited or in love ?
I do not think lack of self control is directly related to gender itself. Perhaps men are brought up in a different way from women or it is socially more acceptable for men to react differently. Some people may argue that men have higher testosterone levels that may influence impulsive and aggressive behavior but I believe men like women are both capable of controlling themselves.