Adam Levine on what he has learned Coaching 'The Voice & # 39;

Adam Levine admits that before appearing as a coach The voicehe never considered himself a mentor material.

"It was this single guy who had never thought of helping anyone in his career because I was too focused on myself," he says in PEOPLE's 15 seasons of the voice special edition.

Levine, who is currently fighting with coaches Blake Shelton, Kelly Clarkson and Jennifer Hudson to create his perfect Voice According to his team, the deepest thing he learned in the series came early, when he realized he had an area of ​​expertise.

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"I had to grow a little bit," said the 39-year-old rocker, "working and providing service to others, teaching them things I knew and playing this crazy game.

Coaches tell everything in the new special edition of PEOPLE, 15 seasons of the voice, now available on Amazon and everywhere magazines are sold.

Facilitator Carson Daly thinks Levine is "crazy" to think he can not teach others, while Shelton agrees that his stuffing buddy had some work to do.

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"Can I focus on" growing up "?" He said.