This has happened to all of us. 

We got an interview or job offer, and then for whatever personal or professional reasons holding us back, we decided to pull out. Usually as a great headhunter, I was nevertheless able to convince my candidates not to say no to themselves, but in the rare cases it happened, I was able to help my candidates get back into the process. 

Here is how you do it. It's not hard but it's not easy...