1. Make the hard stuff easy (maybe by providing some preliminary
practice time, or by rephrasing it).
2. Make the easy stuff hard (maybe by asking awareness question, or
requiring a new twist).
There are many ways we do this, and every student is different. When
it is too easy, it is boring. When it is too hard, they are defeated.
I recently told a six-year-old, "I noticed that you seem to enjoy
solving problems." Just that simple comment helped her focus a bit
more.
Marvin