Damn dude, what do you do when you don't have a girlfriend? Sounds like you have some old Victorian sexual repression issues.
Marijuana, in my opinion, is not at all inherently bad... The brain has Cannabinoid Receptors, even though THC isn't naturally secreted by the brain - a similar substance that causes similar effects is. (a good Wiki article on it is here: THC
Occasional smoking with good company really makes for some good memories (around a camp fire while camping, with some slow guitar being played in the background...), so I fail to see the harm in it with disciplined use. I actually think it does have a positive effect on my personal development in those instances, because my enjoyment of the company and surroundings is heightened; I often have very deep and philosophical conversations under the influence of marijuana.
While I agree that any state or experience should not be dependent on a substance - the substance itself will have a very specific and unique signature that can be a positive addition to similar states that are elicited through direct and deliberate states of consciousness NOT under any sort of external influence.