Why is that by merely wanting something, we somehow repel it. I doubt it would be possible to quantify this effect under laboratory conditions, but what human being wouldn't agree? You only have to really want something for it to all of a sudden become elusive. Late for work and need the bus to come quickly? Need a taxi to the airport? Have a job interview and really want them to call you back? Waiting for a phone call from a potential suitor? Somehow we know that all these situations are prime candidates for frustration and anger.
It may seem like superstition, but it is a fundamental truth in life that by attaching ourselves to an outcome we lessen or even significantly reduce our chances of happiness.
The religions of the Indian sub-continent have harped on this idea for thousands of years. The Upanishads, the Bhagavad-Gita and the Buddhist Sutras all continually focus on relinquishing desire and attachments to people, feelings and things. They tell us to not to attach ourselves to the outcomes of our actions, just act freely. They assure us that this is the path to happiness and even enlightenment.
While these ideas "feel" very Buddhist they are just as much Hindu, the mother of Buddhism. Houston Smith in his wonderful work The World's Religions writes eloquently how Buddhism was born out of Hinduism only to be slowly absorbed back into it on the Indian sub-continent.
There is one very simple and important question to ask about the teaching of non-attachment, is it simply a safer bet? By not putting your eggs in any basket are you simply assuring that none get broken? Is it in effect a coward's path? It is not. It is the path of death, of transformation and of spiritual growth.
Non-attachment goes much deeper than just "being okay" with what happens. The key to understanding the concept of non-attachment is to focus on what is attaching itself to things, people and ideas. Becoming aware of attachment is the beginning of true consciousness. The ego is what is attaches itself, it is the glue. There is no psychological pain, frustration, heartbreak, anger or hate that the ego is not completely responsible for. The path to redemption always begins with discovering that we aren't who we really we think we are. The hero is never really the child of his "parents", he always winds up being some else's child. This is mythologies way of indicating that we are not the ego.