Sorrow loss or failure of any kind leads to depression that is unavoidable for even the toughest lot. Only the one going through that phase of life can feel the actual pain and anger. When the mind fills with sorrow and pain we often end up sympathizing with ourselves or rather pitying ourselves.
Sorrow is a part of love. Loving and losing someone or loving and being not loved back often leads to misery in love. But you can still get over bad times and have a happy life.