In writing, persistence is the line separating success and failure. The same holds true in all fields of life, at least from my limited experience up until this point.

If we give up to small obstacles, we will learn to give up to larger ones. If we persist after small failures, we will not be dismayed at the larger ones. Everything is baby steps, for better or worse. In other words, the snowball effect works on the way down, certainly, but it also works on the upward path.