Expectations are one of the biggest reasons people feel upset, irritation and frustration.
Most of the time, we do not express our expectations clearly to others, often thinking that if they know us well enough, they should already know what we expect. The truth is, no matter how well someone knows you, no one knows what you expect from them unless you specifically tell them and precisely define your expectations. But because it's not the norm to talk about our expectations, we don't...or at least not until others have failed to live up to them, or vastly exceeded them.
Think about it. What are some scenarios in which you get upset, irritated, frustrated, or perhaps even angry?
If you look at what triggered the undesireable feeling, you'll likely find there was an unmet expectation.
So what's the solution? It would be nice if we could eliminate all expectations, but I think that's unrealistic. But what is realistic is to be aware of our expectations and express them, so there's a greater chance they'll be met. It's also important to understand where expectations come from, which is discussed on the CD.