Once you've met your goal, it's time to move the goalpost.
For example, let's say you're trying to get your bug count under 50. When you meet that, it's time to move the goalpost. Celebrate your goal however you like (our team is very food-oriented, so it's usually muffins or cookies or something). Then move the goalpost. It was 50? Now get it under 30. Oh yeah, and stay there for some period of time.
When you meet your goals, go ahead and celebrate. Then move the goalpost. After all, goals aren't about easy; goals are about accomplishing better things.