Plans must be comprehensive to avoid losing sight of one thing while tending another.
Tips
history
From Feng Menglong's 东周列国志 (Ming): the military stratagem of splitting an army and attacking from multiple directions forces the enemy to 顾此失彼 - defend one front and lose another. Still common in strategy and management writing.
grammar
此 ('this') and 彼 ('that') work as a pair, an abstract 'one thing vs. another'. They do not take concrete referents; you don't say 顾这个失那个.
