Never give up!
We may have a different purposes. The target may be an aim to which we must aim and hit, but it may be something what we want to do, something big. Usually, to choose a purpose isn't easy, though, we often say, "If I was able to do that".
My personal opinion is, to say, "I'll do it!" actually easy. And from that moment to try to do it, it is not difficult too, if you do not trying to do everything at once. Me, too, was starting something by simply saying that "I'll do it", but besides that I said "I'll do it", I started to do it.
Remember what you were in the first grade. After all, the most of you wasn't grade 100 in the exam of mathematics, in which all questions were XX + XX = XX. There is always a weak start, and if we are still go on, do not give up just because it turns out badly, or because there are too many obstacles on the way to the target, then the result will be good.