Quote from wrbtrader:
Sports Analogy - Pretend you're a good quarterback (a.k.a. trade signal)...you will lose all your football games if your teammates (market experience, psychology of the trader, discipline, money management, proper capitalization, position size management, stress management, proper broker platform, proper trade workstation, proper trade environment, team collaboration et cetera) don't do their job (a.k.a. trading plan). Therefore, it's impossible for a good quarterback to overcome or compensate for the poor performance of those on his offense or defensive unit in order to consistently win football games.
Says all that needs to be said.