Roy Keane accepts he overstepped the mark towards the end of his Manchester United career.
The Irishman's trophy-laden 12 years with The Red Devils were brought to an abrupt halt last autumn after he was critical of his former team-mates.
He was let go by United and finished his playing career with a spell at boyhood heroes Celtic, but returned to football on Tuesday by being unveiled as Sunderland's new manager.
Reflecting on his departure from Old Trafford, the 35-year-old concedes his forthright views cost him his United career.
"No doubt over the years I have crossed that white line and it has probable cost me lots," Keane told a press conference on Sky Sports News.
"The World Cup in 2002, my United career.
"But it has also been a big plus to me. I do care about the game, who I am playing for and playing with.
"Over the forthcoming days, weeks, months and, hopefully, years at Sunderland I will look to get the balance right.
"Sometimes it comes with experience as you get older and more wise.
"I've made mistakes, but I'm just glad I've got this opportunity and hopefully I'll make the most of it.
"I wouldn't be sitting here if I thought I couldn't do it."
Keane has already been in touch with his former United manager Sir Alex Ferguson and admits he could be on the phone for new players.
He added: "I spoke to him briefly over the last few days, but you've got to be your own man.
"I always enjoyed the way he looked after players, in terms of backing them and defending them.
"Again, maybe I did cross that line towards the end and I was rightly punished for it you could say. Again you move on.
"I was very, very fortunate to play under him and I'm sure I can pick up the phone any time and he'll lend me a few players if I need any!"
Keane has also had his differences with Niall Quinn in the past, but the ex-United captain feels any problems have now been laid to rest.
He continued: "I think it will be fine. A lot of people have been making a big issue of what happened in the past.
"When I met up with Niall three or four months ago, we sorted it out there and then, despite what was going to happen if I took the job or not, which was important for me.
"People have this impression of me out there, but I think it's important to move on.
"I have had differences with thousands of people, but I'm humble enough to apologise if I've done something wrong.
"Working with Niall I really don't see a problem."
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