Bryce Courtenay said this quote
“ Cleverness is a false presumption', Doc had explained, 'it is like being a natural skater, you are so busy doing tricks to impress that you do not see where the thin ice is and before you know, poof! You are in deep, ice-cold water frozen like a dead herring. Intelligence is a harder gift, for this you must work, you must practise it, challenge it and maybe towards the end of your life you will master it. Cleverness is the shadow whereas intelligence is the substance. ”