It depends on the relationship with that guy that you have.
Yes it can be seen as a state of mind. Women need to really face facts about how a man's body will respond to the visual cue though. The fact that men are differnt from us ladies is something we need to consider. In doing so we are protecting ourselves as a couple.
I had a guy ask me to go with him to the mountains where I would be sleeping in a tent in the snow when I was 18, 19. I knew what that implied. It was 1976-77 before the advent of HIV and so many STD's. It was during the explosion of FREE LOVE into the dating scene and the disco era was beginning. The idea was to go cross country sking. Which would have been so much fun.. I was not very happy as to what the sleeping in a tent implied. I did not go and would not have been allowed to go and I do not regret that at all.
It does not take much maturity to have sex. It takes thought and mature thinking to reason the issue out and to make prudent decisions.
You have to know your partner/friend/date.
The only part of this response I will differ with is the first sentence: the nature of the relationship oesn't matter at all (unless he is your husband). While it may be anticipated that temptations will be greater between two people who are attracted to each other, there is no guarantee even platonic friends will be safe from same. In some ways the risks are higher because the platonic friends may let their guard down, assuming nothing will happen. Heck, if it can happen to Hawkeye and Houlihan it can happen to anyone!