So I've come to the realization that I have a habit of not directly approaching attractive women on the street. I'm comfortable talking to women once a commonality have been formed (at work, through friends, social group, etc.), but am extremely hesitant to walk up to a woman on the street and start a conversation.

I can maintain easy-flowing, interesting conversations with extremely attractive woman, with strong eye contact throughout. But I cannot seem to find anything even remotely logical to say to spark a conversation with them in public.

Any ideas why or how to overcome this?