Villas-Boas was part of Mourinho's backroom team for seven years, working as a scout for his Portuguese compatriot at Porto, Inter Milan and Chelsea.
But Mourinho refused to elevate Villas-Boas to a more senior position at Inter, and the 35-year-old decided to go out on his own and enjoyed success as Porto boss before going on to manage Chelsea and Tottenham.
The pair will be in opposing dugouts for the first time this Saturday as Mourinho takes his side to White Hart Lane, and Villas-Boas is adamant he made the right choice to part company with his mentor.
"I don't lose any sleep," said the Spurs boss. "Our break-up point was because I was full of ambition to give him something extra and I wanted further involvement from the job I was doing at that time.
"I felt I could give him much more. But he didn't feel the need for somebody near to him or in another position as an assistant, and because of that it was decided that it was time, after Inter Milan, to continue our careers (apart)."
Villas-Boas also believes he can no longer consider himself a friend of Mourinho, adding: "We had a great personal and professional relationship before that we don't have now.
"I don't think we need explanations. But our relationship broke down. I think we have the mutual respect for each other and we understand what we have been through cannot just disappear, but it's not like it was before."
Villas-Boas also believes that Chelsea consider Spurs a dangerous threat to their title ambitions after Mourinho signed Willian from under their noses and also rejected Tottenham's approach for Juan Mata.
"I suppose that is a sign of evolution from Tottenham and our ambitions," he added. "It is normal. Last year we were fighting for the same objectives in the end so I suppose they wouldn't like to strengthen a rival."
I wonder how desperate the media are to rake up some dirt between the two. If I was either of these managers I would make out we were best buddies just to annoy the media.- crowsy