Slog/sweat/work your guts out
Definition 1 of 2
Pro Tip 1/3Intensity
The phrase indicates a very high level of effort, going beyond the average workload. 
During tax season, accountants often work their guts out to meet deadlines.
Pro Tip 2/3Emotional Stress
Using this phrase can express emotional stress from extreme efforts. 
She slogged her guts out during the competition and felt utterly drained afterwards.
Pro Tip 3/3Physical Exhaustion
Often used to describe physical exhaustion resulting from hard work. 
Construction workers sweat their guts out in the summer heat.