Before we moved to Kansas, my husband worked for the city government in the California city we lived in. They had a no injuries at work reward program in place. If they went 90 days without a work related injury (which didn't happen often because the streets division was in his department and they worked with heavy equipment), they earned ice cream.
Today Buddy spilled his milk. As I cleaned it up, I thought, "we haven't spilt milk in quite awhile, we should have a reward or something for going so long without spilling milk." But then I don't want to punish them for spilling their milk. As frustrating as it is (we have carpet under our table), I have to remind myself that, according to my own mother, I spilt my milk at one meal every day for about a year of my life when I was three years old. So every time I get angry and frustrated at my kids for this, I follow it up by telling them about me as a three year old to help make them laugh and soften my angry response.