Semen production goes on in the testis for 24 hours and gets stored in seminal vesicles. Now imagine seminal vesicles as a water tank. 24 hours production at some time, will make tank full. Its storage capacity runs out. Now overflowing mechanisms take place like night falls and seminal discharge in urine. To avoid this u need to have sex or masturbate regularly. Penis is made of muscle tissues which requires regular exercise for good blood flow. Masturbation provides it with that exercise. It does not cause any illness or weakness.there are taboo regarding it that 100 drops of blood equals to 1 drop of semen. It is totally wrong. Energy from 1 ejaculation can be compensated by 2 biscuits only.