When you are sorrowful look again in your heart, and you shall see that in truth you are weeping for that which has been your delight. Some of you say, "Joy is greater than sorrow," and others say, "Nay, sorrow is the greater." But I say unto you, they are inseparable. Together they come, and when one sits alone with you at your board, remember that the other is asleep upon your bed. Verily you are suspended like scales between your sorrow and your joy.
There is little that separates humans from other sentient beings - we all feel joy, we all deeply crave to be alive and to live freely, and we all share this planet together.
If you practice in accord with your individual capacity, little by little you will find more pleasure and joy in it. As you gain inner strength, your positive actions will gain in profundity and scope.
When doubts haunt me, when disappointments stare me in the face, and I see not one ray of hope on the horizon, I turn to Bhagavad-gita and find a verse to comfort me; and I immediately begin to smile in the midst of overwhelming sorrow. Those who meditate on the Gita will derive fresh joy and new meanings from it every day.