Steve McClaren has blamed speculation over the Newcastle United job for his dismissal at Derby County.
McClaren this week returned to the iPro Stadium as manager – 17 months after being sacked by the club.
The 55-year-old was dismissed after Derby failed to make the Championship play-offs the season before last.
The club's promotion challenge crumbled amid speculation linking McClaren with the job at St James's Park.
After his sacking, McClaren went on to join Newcastle as head coach, though his tenure proved to be short-lived.
McClaren was dismissed in March after a disastrous eight months in charge at United.
Reflecting on the events that led to his sacking at Derby, McClaren said: “I am a very, very lucky person.
"I feel very lucky – very honoured – to be given the opportunity to come back.
“My mistake was not quashing that (the Newcastle speculation), not dampening that, and not committing. That is my fault and I apologise for that.
“By the time I had committed to the club, the club had every right to sack me, and they did. I could have no qualms about it.”
McClaren has acknowledged he needs to build bridges with Derby's fanbase.
“Absolutely, and I can understand it," he said. "As I said, I failed to quash that, calm that, and that was my mistake. I did not do it quickly enough and, by the end, it was too late."
McClaren succeeds Nigel Pearson at the iPro Stadium.
Derby are 20th in the Championship ahead of tomorrow's home game against Leeds United.