A leech that will not quit ...

A leech that will not quit the skin until sated with blood.
A leech that will not quit the skin until sated with blood.

Quotes from the same author

Adversity has the effect of eliciting talents, which in prosperous circumstances would have lain dormant.
A heart well prepared for adversity in bad times hopes, and in good times fears for a change in fortune.
Begin, be bold, and venture to be wise.
Men more quickly and more gladly recall what they deride than what they approve and esteem.
Help a man against his will and you do the same as murder him.