Quote from the book "Agnes Grey"

The human heart is like india-rubber; a little swells it, but a great deal will not burst it. If "little more than nothibg will disturb it, little less than all things will suffice" to break it. As in the outer members of our frame, there is a vital power inherent in itself that strengthens it agains external violence. Every blow that shakes it will serve to harden it against a future stroke; as constant labour thickens the skin of the hand, and strengthens its muscles instead of wasting them away...