The Yogi gets control over the astral nature of semen and thereby prevents the formation of the very fluid itself. You will have to be very careful of reaction. The senses that are put under restraint for some months, or for one or two years, become rebellious if you are not always vigilant and careful. They revolt and drag you out when opportunities arise. Some people, who observe celibacy for one or two years, become more passionate and waste the energy considerably in the end.
Some people become incorrigible, moral wrecks also.
You must not labour under the delusion that you have eradicated lust completely by adjusting the diet a bit, by practicing Pranayama, and by doing a little Japa, and that you have nothing more to do. Temptation may overcome you at any moment. Eternal vigilance and rigorous Sadhana are very essential. You may be able to stop copulation for months and years, but there should not be any sexual craving or attraction for the opposite sex. The state of mental celibacy must be kept up even amidst temptations and sickness.