Ay me! what perils do environ The man that meddles with cold iron! - Samuel Butler

As the ancients
Say wisely, have a care o' th' main chance,
And look before you ere you leap;
For as you sow, ye are like to reap.

Like feather bed betwixt a wall
And heavy brunt of cannon ball.

They who study mathematiks only to fix their minds, and render them the steadyer to apply to all other things, as there are many who profess to do, are as wise as those who think by rowing boats, to learn to swim.