John Piper posted this yesterday at his Desiring God Blog —
LARGE SAILS AND LITTLE BALLAST
Large spiritual passion with small doctrinal understanding is large sails and tall masts on a tiny boat in high winds. It will dart wildly over the surface for a hundred yards. Then one wave, or one crosswind, will bring it all crashing into the unforgiving sea.
Give as much attention to enlarging the depth of your ballast as you do to the height of your sails.
Of course, if you are a sixty-ton flat-surfaced barge, with a broken engine, pray for God to give you sails and wind.