There was this old saying that goes "You should learn from your mistake".
We always learn new stuff every minute of the day. We always make mistakes. Sometimes we learn from our mistakes and look for another solution for the problem. Sometimes we try and try the same solution, despite failing everytime we try it until it finally work.
The solution might not work the first time but after a few times it might work. If that is the case, when do we stop trying and move on to solve the next problem? Had Edison stopped and move on to the next solution, the invention of the light bulb would be years away.
Now things gets more complicated in relationships. Each person we go out with have a different personality. What would be a probable solution to the previous relationship might be a total failure to the current relationship.
I guess in life we are bound to make mistakes anyway... wether we learn anything from our mistakes or not is a different thing afterall. We have to chart our own learning curve be it linear or exponential.