花心血

花心血

Literally means:

spend much time and energy on something

Actually means:

make great efforts to do something

It figuratively means spending time and energy (on sth one desires to accomplish) What takes much time and energy to do is usually something of great difficulty and importance. So this phrase connotes it is uneasy to accomplish something

比喻花费时间和精力（去想办法做成某件事情）。需要花心血的事往往是比较大的或重要的事。含有做成某事并不容易的意味。