Try this exercise .. This also emphasis the important of keeping a field note to jot down the experiences you had in a given day with women!
Seems you r not that much concerned about getting rejected but rather how you respond after being rejected that eats you. Here is the thing, since you have haven rejected many times you are in a much better position to do this.
take some time off and note down the rejections each and every time what happened. What kind of a rejection was that. ( in General, If you are an above average looking guy, even a rejection becomes a polite interaction and you will have easier time dealing with it. But however rejections are cold mainly because she is not available at the moment for your approach. Can be tons of reasons god knows why so; And never approach girls from behind, it spikes cortisol level in girls and put them in a defensive alert state not so good for you my friend

So instead approach from and angle / side / not from front as well. Then see how it goes. )
Back to the topic -
now once you note down the rejections then you note down how you felt and how you acted following the rejection. Once you start noting down that you will soon stat to see patterns of you behavior and you will have a third-person view of how things went. This is the point you want to approach first because what it does is, it puts you into a stat of self-awareness.
Now comes the best part -
Now what you do is you create a scenario in your mind how you should have acted when you got rejected each time. Visualize it and make it absolutely clear in your head the way you acted. ( consider everything you felt and experienced in reality to form the solution more robust ) then note it down. Rehears it, commit it to your memory. And next time you are in the field, before you approach a girl load it back to memory as a fail-safe mechanism. This way you have a much better chance dealing with the situation without too much fuss provided you got rejected. Learn about Rejection and why it happens, increase you understand on human behavior, then you will come to know why its not something you should take personally and its not your fault and adjustments you need to make for yourself in order to minimize rejections.
Ps - your aim in this exercise is to ultimately build your composure. It means, increasing your smoothness, calmness, building your zen even the world around you falls apart.
Peace.!