Letting go of expectations does not mean adopting a defeatist attitude - no, not at all. There's nothing wrong with being optimistic! Of course we want to maintain a positive attitude throughout our approach to our lives. The opposite to that would be to engage in catastrophic thinking which often becomes a self-fullfilling prophecy. The problem with expectation comes when we have to have a certain outcome in order to be okay. Here's an excerpt from a little article called, "Psychological Benefits of Meditation" that expands on this:
"Meditation frees persons from tenacious preoccupation with the past and future and allows them to fully experience life's precious moments", says Daeja Napier, founder of the Insight Meditation Center and lay dharma teacher of insight meditation in suburban Boston.
"Many men and women tend to live in a state of perpetual motion and expectation that prevents them from appreciating the gifts that each moment gives us," says Napier. "We live life in a state of insufficiency, waiting for a mother to love us, for a father to be kind to us, for the perfect job or home, for Prince Charming to come along or to become a perfect person. It's a mythology that keeps us from being whole.
"Meditation is a humble process that gently returns us to the now of our lives and allows us to wake up and re-evaluate the way that we live our lives," says Napier. "We realize that the only thing missing is mindfulness, and that's what we practice."
The kind of expectation that leaves us in a perpetual "state of insufficiency" is the kind that is unskillful. Let life unfold. (It will unfold whether you "let it" or not!) Stay open to whatever is. Remember impermanence. And in all things cultivate compassion - for yourself and for others. This way we will be at peace with ourselves and in a state of inner harmony no matter what.