Rather than having an expectation, have no expectation. Don't have an expectation, and you won't be disappointed at a different outcome. Don't have a desire, and you won't be unhappy when it goes unfulfilled. Don't expect the sun, and the clouds won't make you sad. Don't desire pleasure, and you won't feel cheated when you receive none.
Aside from your feelings, you can of course change things in your life if you want to. You can right a wrong, improve your standing, paint your room green, move to a new city, whatever. But don't do those things in order to chase a feeling of happiness; that's a dog chasing its tail.