"נקי יהיה לביתו שנה אחת"
The Torah says that for the first year of marriage one should be home with his wife ["clean to his house"] and not go out to war.
The Sfarim explain that one should also be "clean" of personal pleasure. Especially in the first year of marriage, many chassanim tend to take advantage of their newfound permission to be with a woman. After 20 plus years of abstinence they finally have the opportunity and it is permitted. No guilt! A MECHAYE! So they overdo it.... The pasuk says "be clean to your house" i.e. wife. It is NOT about your pleasure and lust רחמנא לצלן.
Be Clean. Be Pure. Think Holy.
The Kotzker says that this first year is the base. After the first year one must continue on this path of Kedusha.
