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In an interview with an American radio station, Megadeth frontman Dave Mustaine spoke about demanding a lot from himself, and therefore being considered a difficult person to work with. Check out his statements:
“Part of the reason I’m difficult is that I demand the best I can from myself, and I think when you do that you end up expecting the same from other people. I think a lot of times when I say 'no' to people, they misunderstand. It’s not that I’m saying 'no, get out of here'."
It's more along the lines of 'no, I think we can do better' or 'maybe not now'. But often people don't like rejection. I certainly don't. I don't know, maybe it's okay for you but it's not for me. So when I say 'no' to people a lot, they get angry. I remember the first time I asked a girl to a school dance and she said 'no', I thought 'I'm going to tell everyone who you are!'.
“To win, you have to surround yourself with winners. If you let everyone get away with anything, you get what you deserve. Part of the reason I’ve been successful for the last 35 years, that I’ve had two great bands with almost one hundred million album sales, is because I really demanded a lot from myself.”.