If you need to be promiscuous, be promiscuous, it may make you feel guilty, but it also might provide the spice missing in a marriage you otherwise might find unbearable. If you deny your need for promiscuity and not accept it, it will come and get you anyway, and devour you. If you need to smoke, then smoke. Better to aggress a little against yourself than a whole lot against others. And so on through all the so-called vices.
Nobody can be all good all the time.
Those who try become tyrants of the worst kind, turning their self-destructive impulses into destruction of others. History's worst evils have always been committed in the name of the highest good. The best non-holy people can hope for is that by allowing a minimum of bad into their lives they can preserve a maximum of good. A truly good non-holy person must have some bad in him, or he will never have compassion and the ability to forgive others. Perhaps you are forcing yourself into a role that your essential, basic personality never bought into.