Since there are at least two unwise ways of doing something for every wise way, the existence of of seemingly contradictory proverbs is not only unsurprising, but inevitable.

Proverbs are meant to promote wise behavior. Wise behavior often exists toward the middle of a behavioral spectrum and is flanked by unwise behaviors on either end. For every wise mode of behavior there are two opposing unwise modes. For example, responsible frugality is flanked by miserliness on the left and spendthriftness on the right.

"Look before you leap" and "take the bull by the horns" are proverbs which seem contradictory, but really aren't. One addresses the problem of rashness while the other addresses the problem of indecisiveness. Rashness and indecisiveness are opposite but equally defective modes of decision making. The two proverbs are both meant to steer one away from opposite but equally undesirable extremes and toward a more reasonable and prudent middle.