Underlying Assumptions

When speaking, it is important to not assume that the other party understands the underlying meaning, especially when they are not native speakers of the language.  Much of our everyday conversations are based on mutual underlying assumptions.  That may not work in giving instructions.  For example, consider the following: 

“My therapist told me to write letters to the people I hate, and then burn them.  I did that, but now I don’t know what to do with all the letters.”