Experiment, and don’t make the same mistake twice
The best investment I've ever made is in building my own confidence. What I've realized is that I'm willing to do things and learn, to get kicked in the teeth as long as I don't make the same mistake twice.
Source: Sales author/consultant Jamie Shanks
There's no way around it in sales, you have to be willing to experience rejection. It's going to happen (multiple times), no matter how skilled you are. But it's in how you react to new information and the results of your experiments that will go on to define your future.
Experiment, try new things, but don't do the same thing over and over again if it's not working, expecting different results. Fail, pick yourself up and become a little better. Invest in your own confidence and realize that you can do this.