My girlfriend advises me not to masturbate because it causes loss of sensation during real intercourse, but I find this act increases arousal, so what is an appropriate frequency? (Tung, 25, Ha Noi)

A 21-year-old student, who has been masturbating almost daily since age 16 and cannot stop, wonders if frequent, long-term masturbation can reduce sexual function. (Minh, Phan Thiet)