If you can, you should try to avoid expecting something in the first place.
This isn't always possible as most of the time its almost a sub-conscious thing. So, when you realise your expectations have been dashed, or realise that you DO have an expectation work through WHY you are feeling the way you are feeling.
Why you expect/expected it.
And then look to why you are letting it affect you in the way that it is.
If you can do this, hopefully you'll find that sense of balance again.