my favorite...
"There have been joys too great to be described in words, and there have been griefs upon which I have not dared to dwell; and with these in mind I say: Climb if you will, but remember that courage and strength are nought without prudence, and that a momentary negligence may destroy the happiness of a lifetime. Do nothing in haste; look well to each step; and from the beginning think what may be the end." Edward Whymper, Scrambles Amongst the Alps