It is more in our nature to be happy and not in sorrow; but the reality is the reverse: We are more in sorrow than in happiness. That is because we are too lazy to act and maybe even ignorant of the circumstances, and hence not in a position to deal with it.
'How to have Courage,
Calmness and Confidence' by Paramhansa Yogananda, tells us the 'why' of it. Despite our innate nature and ability to be happy, we forget to seek the means to be peaceful and happy. The guru says that "sorrow has no objective existence but if you go on affirming it, it can exist. If you deny it in your mind, it will disappear. "That is what I call the hero in man: His divine nature." Our soul is pure and its attributes are all positive -success, good health and wisdom. The moment one identifies oneself with poverty of thought and good habits, one drifts towards misery. Lack of willpower makes one see even the slightest irritants as insurmountable obstacles.
Don't we say, everything remaining same, the winner is the one conscious of the 'facts' surrounding him and in a position to deal with them? But if one focuses on solving one's problems, they seem to disappear.
If one is in a position to play up one's heroic nature, then fear or sorrow will always keep away. One must always keep in mind that as long as the conqueror in mind is kept awake, no sorrow can visit one.
Nature has an automatic way to let you bounce back. In other words, as the guru says, one must assert one's heroic self to stay a winner in life.