Just don't put a ended sentence at the end of something that is not yet a finished utterance.

It's always possible to make a full sentence quotation after a colon, possibly using indentation:

  With just enough of learning to misquote.
    — Lord Byron

This can be even more explicit:

  “One whom it is easier to hate, but still easier to quote.”
    — Alexander Pope

Or you can also opt for inner quotation lightly altering the typography, like “quotation is the highest compliment you can pay to an author”, which is actually an excerpt from the wider quotation:

  “Quotation is the highest compliment you can pay to an author. Perhaps the next highest is, when a writer of any kind is so considerable that you go to the labor and pains of endeavoring to refute him before the public, the very doing of which is an incidental admission of his talent and power.”
    — Anonymous