$20k/day x 250 trading days per year is $5 million. 250 trading days assumes that one never takes a vacation or a sick day, which in my experience in working with other traders is either very rare or unrealistic. Typically, if a trader says he makes $x/day, then it is the average that he makes with both his up and down days.
Make a sticky and stick around your screen (or somewhere that is easily seen). It helps! Remember, discipline is your friend. Non-discipline is your enemy. So why not be disciplined!