Whatever need he is presently filling means more to you than the fact you know it is wrong.
You need to take a hard look at yourself about why you need [whatever he gives you] and either 1. decide to need it less or 2. get it from someone else (more appropriate).
Usually tho, your need represents a deeper problem. Rather than fixing the problem, you use this guy as a distraction. He's like a drug keeping you from improving yourself. Time to get off the needle.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh