Describe a time when you tried to do something but weren't very successful. You should say: when it was what you tried to do why you were not successful in doing it.

It was five years ago when I wanted to travel to the US, but I wasn't successful, so I was wondering why that was. I was told in the rejection letter that I was supposed to have a certain amount of money in my account that I couldn't or would not be able to sustain [...]