Achievement of any kind is the result of our thoughts.
It is the pure thought that give us 'Wings to Fly'.
As we all know that thoughts process is a regular process and therefore we should always try to maintain the pure thoughts in our mind.
If after attaining the success, our thoughts start getting weak of impure, we will start falling.
James also emphasized that the achievement is also directly proportional to sacrifice. If your sacrifice is high, your achievement will also be high.