It happens, and it will happen again. Learn to not invest yourself so early in a relationship and learn to not dwell on your rejections/failures. Have you ever seen the jerks picking up so many women? I'm sure you have. It happens that way because the jerks don't invest themselves emotionally and it allows them to be confident and relaxed. Don't be a jerk, but learn from the way they operate. Don't get all wrapped up in one woman unless you know for certain that she feels the same about you.
...one can be sure of nothing until it has already happened...