How can we be happy if we are swinging to a past that is gone, and a future not yet born? Happiness belongs to the present moment, it belongs to the 'now'. That is why this moment is called the present.
Those who learn the art of happiness, learn the art of being conscious in this moment. They don't let the monkey mind swing to yesterday creating regret and worry, just as they stop the monkey from jumping into the future with fear stress, and anxiety. They cut the monkey's tail and make the monkey mind into a monk, still, Peaceful and Blissful. Unfortunately, we are unable to live like a Peaceful monk in Nirvana. We live like a monkey going from here to there, from thought to thought, and we lose the Bliss of the present moment.
Very few people realize the secret, that happiness is in the 'now'. They live life moment by moment, in Peace and Bliss, enjoying what life has to offer. There is so much beauty around us, so much Divinity, if only we learn to count our blessings and enjoy what life has to offer, if only we surrender and accept life as it unfolds moment by moment, we can be happy for the rest of our life. Remember! You must be happy in the 'now'. Don't trade your happiness with yesterday and tomorrow.