Most doctors can't remain as open and sensitive as they would like and still survive the stress of patient care, so they protect themselves by putting up an emotional wall and becoming detached. The longer a doctor heals people, the more callused he or she can become in the process of such service. As Rabbi Lamm points out, even something as simple as helping an elderly woman across the street may do the trick. A certain level of callousness is essential to survive in business. For example, it's helpful not to have a melt down every time a customer complains or you don't make a sale.
Success requires having the stamina to stay in the game long enough to succeed.
Repeated use of that area of the body toughens the skin. It wasn't easy for lots of sales professionals in the beginning of their careers. But steady rejection, if it doesn't kill you, will make you stronger. You'll realize that rejection isn't as big a deal as you've been making it out to be. A certain form of rejection callousness is healthy and good for business.