To put in a lot of hard work only to get no appreciation or even face criticism; strenuous and unrewarding.

to put in a great deal of effort for little or no reward; an arduous and unrewarding job

to curry favor by acting obedient or showing off one's good behavior; to toady to

to curry favor or toady; to get a desired outcome by using flattery

To exert every possible effort to win someone's favor; to throw oneself at someone or something to get on their good side.