If you find a girl attractive do you just walk up, try to escalate and if she doesn't reciprocate back it's up to you to decide whether you try again or you just move on. Is there a point in which you could tell this is a lost cause? (I always hear you need to be sexual or at least give that perception of it or else you'd be treated like one of her girl friends.)

(Is it weird that I could do it outside but when near the campus or inside the campus, I just can't. I'd like to think it's because I'm worried what other might think of me in campus or near the vicinity which stops me or maybe that's what I tell myself as an excuse. I was wondering if anyone here had some sort of the same experience in their college life, any advice?)