Take a Break

Sometimes you're having a bad day because you've pushed things past the point of diminishing returns.  When you're tired, frustrated, angry, or any combination thereof, there comes a point where you just can't be effective anymore.  

If you've ever baked bread, you know that the longer you knead the dough, the tougher it gets.  Eventually, it gets so tough that you can't shape it.  But if you let the dough rest, it relaxes and you can work with it once more.

If you've reached that point where your brain is no longer pliable, it might be time to take a break.  If you've got the time, get a good night's rest and tackle your project again tomorrow.  At the very least, take a break for a few minutes.. 

Stand up, stretch, get a (healthy) snack.  Then put your feet up and let your mind and body relax.  It may feel like you're wasting time, but in the long run, you'll save time with your renewed effectiveness.