The art of being happy

I have a co-worker whom I envy... a lot... She is so simple, not worried about how she looks or dresses, always smiling and courteous and seems so happy... She seems to be in her own world, so.... simple. I wish I could be like that... I wonder if her simplicity and happiness came with age (she is an older lady) or if she had some sort of a realization and made peace with life?

The more I thought about it, the more it became obvious that the key to happiness is to let go... of worldly possessions, of silly emotions, even of people. But how does one begin the process of letting go? For example, is being a minimalist (having only what you need, in terms of furniture, gadgets and such) mean you are on the path to Nirvana? How do you let go of emotions? More importantly, how do you let go of human relationships?

Maybe when I have the answers to these questions, I will be as happy as my co-worker :)