Plug away
Definition 1 of 1
Pro Tip 1/3Non-Stop Effort
Use when describing continuous, hard work despite challenges or slow progress. 
Even with the deadline approaching, she kept plugging away at the report.
Pro Tip 2/3No Immediate Success
Implies effort without quick results, often requiring patience and time. 
Although the results weren't showing, he plugged away at his diet and exercise regimen.
Pro Tip 3/3Figurative Usage
Understand it's a metaphorical expression, not related to actual plugs or electricity. 
She didn't understand the math concept right away, but she plugged away at it and finally got it.