Publius Cornelius Tacitus quotes:

Candor and generosity, unless tempered by due moderation, lead to ruin

More faults are often committed while we are trying to oblige than while we are giving offense

Love of fame is the last thing even learned men can bear to be parted from

Be assured those will be thy worst enemies, not to whom thou hast done evil, but who have done evil to thee. And those will be thy best friends, not to whom thou hast done good, but who have done good to thee.