Read a good piece in Zen Habits blog.
I think it goes a bit overboard in praising chaos and criticising planning. But I agree that being comfortable with some unpredictability in day to day life is very important for sustained happiness. We mustn't get too upset when things and people don't turn out to be exactly as per our expectations. As the article says: "We expect others to try to make us happy, to go out of their way to give us what we want. This is not why other people exist."
Let's open ourselves up to life so that it can spring it's own surprises on us. Not the ones we have been expecting. Because if you have been expecting a surprise, the only surprise you can get is not getting it!
Overall, a valuable piece.