It works for push-ups too. Instead of counting to 50, you count 1 through 10 and repeat. And if it gets really tough, just count to 5, and repeat. Even though you might be on 46th rep, but I found it easier to push myself harder if I'm counting 2,3,4,5 instead of 47,48,49,50. And if energy permits, I'll add another 5.
