When you say that the positive tendencies are the cause of happiness in an individual, in the same breath you can say that the negative tendencies are the cause of unhappiness. Well, extreme stress, anxiety and frustration pave a clear way towards depression.
It is the same old story through the ages- the eternal conflict between the Light and Darkness. These two forces can not exist at the same time at the same place. When the Light arrives, we need not order the darkness...