I learned already a couple of times. You try to start an idea, but the idea doesn’t work as expected. You start getting disappointed, mad of the wasted time and so on… In the end it was not useless, because now you learned what didn’t worked.
After something does not work as expected, you have two possibilities:
1. Try it again and try it harder
2. Go on to the next project/idea
Repeat these step after every new iteration.