When most guys think about approaching a woman and starting a conversation, they feel nervous, anxious, and uncertain. The more attractive the woman is, the more nervous most guys feel. This is simply because the more attractive the woman is, the more value the guy in question places on her, in his mind, before he even talks to her. So if he does try and start a conversation, and get rejected, there is a larger perceived loss than if he didn't find the woman very sexually attractive.
The only problem with this model is that it is all in the person's mind. The guy in the above example is putting a huge amount of value on the girl before he even talks to her. So if he is rejected, it seems to him that he is losing a lot.
Because it has been shown again and again in study after study that people are incredibly sensitive to perceived loss, this can be a very hard thing to overcome.
If you find yourself in this situation, the simple way around this is to change the perception. Most guys imagine that when they approach a beautiful woman, they are implicitly seeking her approval. As if she has some kind of higher social value that he does, and therefore she can choose to accept or reject him.
The easiest way around this is to simply value yourself, above all others. After all, you are the most important person in your world, aren't you? When you approach anybody for a conversation, you should certainly give them the benefit of the doubt, but you should never assume they can give you something emotionally that you can't give yourself.
Ideally, whenever you approach an attractive woman, your mindset should be one of curiosity. Does she have a cool personality? Will your personalities match? Will there be enough reciprocal benefit to create a mutually pleasurable relationship?
When you start to develop this mindset, approaching women will become second nature. Then you will be able to use all the tools of seduction at your disposal. And one of the cool things you'll discover when taking on this mindset, is that this is likely more powerful than any seduction technique you can learn.