Humans are a confused concoction of mixed emotions
When the going is good, and you are achieving one success after another, you become very positive about the future. Sky is the limit, and the goals that you set are high. With each achievement and success, your goals become even higher. Your achievements always fall short of the goals. You try harder, achieve more and push your goals even higher. This cycle continues till you either burn out or give up. You feel powerful and confident due to all your successes, but you feel frustrated and unsuccessful as you are not able to achieve your high goals.
When things are not so good, and you have not met with much success, you feel low and disappointed. Your expectations are low and you set very low goals for yourself, always fearing the worst. Your achievements are almost always better than the worst possible. And hence there is always a feeling of relief and happiness at each achievement. You do not feel powerful or confident due to lack of major successes, but you feel happy and successful as you are able to achieve all your low goals.