Do nothing in haste; look ...

Do nothing in haste; look well to each step; and from the beginning think what may be the end.
 Edward Whymper

Quotes from the same author

The thing to be wished for, is not that the mountains should become easier, but that men should become wiser and stronger.
 Edward Whymper
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 naught 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