Some athletes don't understand that being uncomfortable is part of the process of achievement, so they use the discomfort as a reason not to go about it all. Naturally, they then don't get what they want. (Or they don't get what they tell themselves they want, anyway.) We must learn to tolerate discomfort in order to grow!
If we fail to see this, we're essentially training ourselves to ignore our own promise. (My apologies for the play on words here within, but I meant it both ways.) Commitment then means nothing. Just as there is no partially pregnant, there is no "partially committed".
Commitment is not a one-time occurrence. It occurs daily, hourly, continually. We must choose to commit to our goals and dreams, over and over and over.
The test of this commitment, of course, is action.