One of the leading causes of depression and loss of energy is inner accounting. It is a continual feeling of being owed something. Trivial things like feeling grieved that someone didn't greet one, or not take one's phone calls, can make one unnecessarily feel neglected.
This amounts to keeping an account internally with the feeling of not being given one's due, whether it is wanting that others should treat us better or being resentful of one's talents not being appreciated. It causes a lot of negative thinking where one keeps repeating these thoughts, inviting depression and weakness of character. This weakness manifests much more when the chips are down and others do not sympathise with us.
Do we expect too much from life? Do we feel that at some point, we will fulfill all our desires? Desires are endless. When we study history we realise that no one is able to fulfill all their desires, not even Alexander the Great could do so. The more we demand of life, the greater the chances of inviting pain and suffering. Our individual happiness then depends upon the fulfillment of certain conditions by life and when that does not happen a sense of being done great injustice prevails and we feel cheated by life.
The persistence of such thoughts invariably constricts our growth and narrows our vision completely. Suddenly irrelevant and trivial things become very important. If someone did not call me for dinner, it becomes a cause for nurturing deep grievance. We get trapped in a prison of our destructive thoughts of self-pity and resignation.
All religions propound that forgiving all hurts and grievances leads to the cancellation of debts. From the moment we drop the feeling of being owed something, and discard the expectation of being paid back for all we have done to help, all debts get cancelled. If one is able to do this every moment, on a daily basis, harbouring no resentment and staying clear of the expectation of being owed something by life or people, naturally there will be a sense of deep release within. Consequently, the inner freedom experienced of living a burden free life will naturally bring joy and happiness in our lives.