Let me rephrase my question?

Most guys have seen a good looking girl somewhere, whether it be at a bar, a club, a party, in cl, on the street, wherever, and not had the to walk up to her and say hello. So my question is, if you can remember those times you hesitated, what EXACTLY was going through your mind? What SPECIFICALLY made you decide to NOT walk up to the girl and say hi? What did you think you might do or say, or what did you think she might do or say? What fear, specifically, kept you from taking a chance?