In my experience, the most consistent and successful salespeople are pets and kids. Every day, my dogs' passion and persistence conquer my resistance. Both kids and pets understand that every "no" just means "not yet". Both groups have no fear. They look on repetition as a means to an end.
If you want to become a better salesperson, study and imitate your children and/or your pets. Remember, "no" is the final answer only if you let it be.