Rejection is tough on everyone. Good sales people do a few things to mitigate this that I've noticed and practiced. One thing is to think of it as a game to expect a certain amount of rejection as part of what you do in advance.
I mean if I told you right now to pick up the phone and call someone and pitch them and there was no outcome and I paid you $20 to do it you probably wouldn't have a fear of doing that. If I told you that I would pay you if they hang up on you $20 but $0 if they don't you probably would all the sudden not be afraid of the hangup, right? It's all a psychological game. Same thing with approaching a girl in a bar.
Second thing though is that some good sales people don't pick up on social cues as well as others. So they don't feel the rejection as much as sensitive people do. If you are cold calling the same micro expressions that might turn a sensitive person into jelly completely escapes many good salespeople. Same with just a voice. It takes time to get over this automatic reaction but it can be done with practice just like anything else. (Although you don't want to turn it off because the same skill is really good for negotiating.)