When we are given a chance to do something that matters, we do not know if we will ever get to do it again, at least for sure. So why leave it to chance. If it matters to you, do it with full intensity. Do not worry so much on getting it right. Leave that for another time. Do what you know is best at that time and see what happens. Even if it does not go as you have intended, at least you know that you have done it with your fullest intensity.