From the Persistence Files  

There was a salesperson named Alex who worked for a marketing firm. Every month, like clockwork, he would make his rounds, calling on potential clients to pitch his company's services. 

One of these prospects was a man named Joe. Joe ran a small business, and for over five years, Alex diligently pursued him. However, each time he reached out, Joe firmly declined, citing various reasons why he didn't need what Alex was selling. 

Finally, Alex had had enough, and made the decision to never call on Joe again.
A year later, Alex was leaving to go work with his wife in her business. Before he moved on, it was his responsibility to train his replacement, an eager (hungry) salesperson named Raj.

As they were going through some of the files, Raj spotted a folder with a big red ‘X’ on the front. "What’s the red X for?" he asked.
Alex sighed, shaking his head. "Oh, that. He’s never going to buy. Don't waste your time. Besides, Joe's kind of a jerk."
A week later, after Alex left, Raj decided to give Joe a call, mostly because he wanted to see if he was as big a jerk as Alex made him out to be.

Raj dialed the phone, and, to his surprise, a woman answered. She explained Joe had recently retired, and she was his replacement. Raj took the opportunity and introduced himself and the company and explained a little about how they might be able to help her. Five minutes later, Raj had scheduled a meeting with his new prospect.

This kind of thing has happened to us, too. (More than once.) So, think twice about assuming a No is forever!