Check that you are clear what is ahead of you before making a decision that you cannot go back on.

The intuitive notion that this phrase derives from the undeniable wisdom of checking a fence before jumping over it on horseback appears to be misguided. Such behaviour is and was common enough amongst riders to have been given a name, that is, ‘craning’. Nevertheless, the proverb as first recorded refers specifically to the rashness of leap unpreparedly into marriage. This proverb is first recorded in John Heywood’s A dialogue conteinyng the nomber in effect of all the prouerbes in the Englishe tongue, 1546:

And though they seeme wives for you never so fit,
Yet let not harmfull haste so far out run your wit:
But that ye harke to heare all the whole summe
That may please or displease you in time to cumme.
Thus by these lessons ye may learne good cheape
In wedding and all things to looke ere ye leaped