Always live up to peoples expectations, but never expect anything from anyone. Seems tough! but it is the key to happiness. No one can ever hurt you until let him/her do so and when you start building expectations you are creating an opportunity for the same. I think this is what is called "detached attachment".
"But how can i not expect things from anyone?" .....good question. After all we are all social beings and live in harmony with each other. One cannot do everything by himself and should not. The point is when someone does good to you be thank full but when some one is not good to you don't complain(of course unless someone harms you). But don't take it to for. You will always find people around you who would be worth expecting from. They would be there for you in all your good and bad times. Those are the bestest people in the world, they are the greatest gift life has given to you, your best buddies. Never ever let them go.

But this mixed theory of expectations can sometimes be very pain full(although it will save u most of the times) because when you rarely build expectations and they are not realized its hurts more, so be very care full.
The theory of expectations can be applied to all sorts of situations.For example when u say "I love x" it is not subjected to the condition of x loving u, is it? You should not feel hurt if "x" does not feel the same way and u are the luckiest person if "x" does feel the same way.
But sometimes you can still be hurt no matter how strong you be in theory.
Is it right on ones part to show you a picture that is not really there. What can you do when one builds up your expectations and then blows them apart. If "x" gives a positive response you are bound to build expectations and then suddenly one day you find that "x" is now your ex.
What do you do now? Be very care full when you expect.