Legendary American football coach Vince Lombardi said mental toughness was "essential to success" and perceived it as "a perfectly disciplined state of mind that refuses to give in".
Football matches are won and lost by small margins. Having the edge mentally can be the difference between tasting sweet success or swallowing the bitter pill of defeat.
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From Sunderland gaffer Gus Poyet knows a thing or two about playing in big games. During his 18-year playing career he won four major honours, including the Copa America, FA Cup, UEFA Cup Winners' Cup twice and the European Super Cup.
How did the former Tottenham and Chelsea midfielder get himself in the zone for these big games? Watch this video and find out....