Some goals have a simple path to success. In order to save $100 you can put away $10 a week, and in ten weeks you'll accomplish that goal. Other goals aren't as easy to predict. There is not always an equation to be followed.
Maybe there is a technical problem with a computer and you need to fix it. Only trial and error is at your disposal, and there's no way of knowing if your third idea or your thirtieth will be the right answer. Or maybe you want to be a public speaker. All the training and practice will hone your skills, but you never know when or if someone is actually going to ask you to speak.
The goals with no hard-and-fast path to success are the hardest to achieve, and many times the most rewarding. Yet sometimes we quit when it's the very next phone call, the next solution that will be the answer. Press on, it may happen a few years from now or it may happen tomorrow, but it can't happen if you quit too soon.