You don't have to depend upon your mood to do something. You can change your mood at will. This can be explained by Theory of Motion creates Emotion. If you observe sad and depressed people - they walk and talk slowly and their body movements are slower. This means that whatever happens to your mind happens to your body. Your mind and body are connected. Very few people are aware that there is this two-way link between the body and the mind.
Consider this: If you are experiencing sadness in the mind, try to keep your body active, by doing some exercises or engage yourself in some physical work. Soon you will experience change in the state of mind.