-Friedrich Nietzsche
Many things can correspond with this quote. Stuff like not eatting right. A high cholesterol diet could kill a person. After they experience that they eat healthier from then on. Things like doing dangerously stupid stuff like jumping off a building or walking in front of a car. People think twice before doing something like that again.
Now on to a more concrete example, like wife-beating or suicide. A woman I know married a man that hit her constantly. he would chake her. This even cost her child's life. After she divorced this man she was wiser when she started dating again. Now whe is married to a wonderful man. I also have a friend who once thought that ther was "no way out". She tried to kill herself three times. The third time she had to be rushed to the hospital. It scared me half to death. whe lived and now she knows that she has loving friends and that there is no reason to leave.
I know there are many, many more examples to fit this quote's description. This is the way humans learn, through bad experiences. That is the only way we survive.