Jessie Fong, here is a video of the song:
http://youtu.be/d-diB65scQU (http://youtu.be/d-diB65scQU)
The great Indian Buddhist master Shantideva wrote in Engaging in Bodhisattva Behavior (Skt. Bodhicharyavatara):
Although having the mind that wishes to shun suffering,
They rush headlong into suffering itself.
Although wishing for happiness, yet out of naivety (Skt. moha),
They destroy their own happiness as if it were a foe.
Due to our ignorance, when we wish for happiness, we are depending on wrong object as the sources of achieving it; we place our happiness on conditioned and transient objects, then we are creating more unhappiness and sorrow instead of creating more happiness for ourselves.
Ultimate happiness is of course when we can eliminate the cause of all sufferings and having the wisdom to see and to understand fully the meaning of the nature of things. As for ordinary happiness in samsara, it is actually a state of mind. Though outer factors do play a role in term of satisfying our 5 senses, the actual 'happiness' in ordinary people is determined by the mind.
Buddhism provides two definitions for happiness. One is defined in terms of our relation to an object, while the other is defined in terms of our relation with the state of mind of the feeling itself.
"The first defines happiness as the experiencing of something in a satisfying manner, based on believing that it is of benefit to ourselves, whether or not it actually is. Unhappiness is the experiencing of something in an unsatisfying, tormenting way. We experience something neutrally when it is in neither a satisfying nor a tormenting way.
The second defines happiness as that feeling which, when it has ended, we wish to meet with it once more. Unhappiness as that feeling which, when it arises, we wish to be parted from it. While a neutral feeling is that feeling which, when it arises or ends, we have neither of the two wishes.
The two definitions are related. "
The key point here is 'Why worry?"
"If it can be remedied,
Why get into a foul mood over something?
And if it can’t be remedied,
What help is it to get into a foul mood over it?" - Shantideva