I met a smart person who had passed every exam he ever sat. I told him he had held himself back from his true potential.
My biggest suggestion is the Peter Principle...
‘In a Hierarchy Every Employee Tends to Rise to His (sic) Level of Incompetence’
If you apply it to life rather than just institutions and companies you can get very interesting insights, as I mention here: Self Help Blog › The Key Life Principle?
In fact these types of principles can be applied to what are usually thought of psychiatric illnesses. My self-help product for people who are chronically stuck with their lives addresses exactly this: Self-Help 'Meeting'... All Ready For Completely Changing A Life Around!
Psychiatry has a little bit to teach self-improvement, but there is much more that needs to go back the other way.