keep at

1.  Persevere or persist at doing something. For example, If you keep at your math, you'll soon master it. It is also put as keep at it, as in He kept at it all day and finally finished the report. [Early 1800s]
2.  keep at someone. Nag, harass, or annoy someone, as in You have to keep at Carl if you want him to do the work, or He keeps at Millie all the time. Also see keep after.

Definition: continue, endure
Antonyms: discontinue, give in, give up