You are not a machine
Some days the outcome is amazing, a high that you need to cherish and the next day as you give your best, the outcome might not be as good or better than the last. This should not lead to disappointment and dejection. It is to be expected as we are not machines, and we have our good days and our bad. We are also influenced heavily by the environment around us and circumstances each day that may not be in our control that will not allow the same.
Enjoying what one does makes it easier to give ones best. When you do not enjoy what you do it is hard to commit yourself to it whole heartedly. So find what is it you enjoy doing and then master that and deliver your best to get the best outcomes.