Castain says the best salespeople turn rejection into a learning experience.

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When he isn't writing, he is running his latest startup, Brainrush, which is trying to turn the process of learning into a game-like experience.

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Instead, why not make the workplace itself into the classroom environment and every work interaction a learning experience?

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Most successful entrepreneurs are not fearless, but they know how to transform these fears into positive actions rather than negative ones, and they take every failure as a positive learning experience.

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"The truth is that the first step to getting a job and getting back into the jobs market is having some work experience and learning to work and turning up for work on time and being part of a relied on team, " he said.

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