Never Eat A Few Days Old Cut Fruits

I wake up with severe stomach pains. It is horrible. I could not figure out what happened or why. I know it must be something I ate yesterday. My Wife immediately remind me that I ate the water melon which was lying in the fridge before I left for China. This is not my first time. I had problems with cut pineapple as well.
Bad bacteria must have developed over time in the fruits even though they are kept in a airtight container. I am the kind who have been taught and trained never to waste food. I must now unlearn what I was taught to make sure this pain episodes do not repeat again. This is umpteened time I was hit. Many times, it was painful but not as severe. A few episodes before I felt I am dying just like this morning.
Friends and readers, beware! Never eat cut/exposed fruits that have been lying in the refrigerator after one day.