The complaining customer ...

The complaining customer represents a huge opportunity for more business.
The complaining customer represents a huge opportunity for more business.

More phrases

All the great things are simple, and many can be expressed in a single word: freedom, justice, honor, duty, mercy, hope.
I know but one freedom and that is the freedom of the mind.
 Antoine de Saint-Exupéry
Freedom is not worth having if it does not connote freedom to err.
The amount of happiness that you have depends on the amount of freedom you have in your heart.
 Thích Nhất Hạnh
Without freedom of thought, there can be no such thing as wisdom - and no such thing as public liberty without freedom of speech.

Quotes from the same author

Your attitude, not your aptitude, will determine your altitude.
You are the only person on earth who can use your ability.
Remember that failure is an event, not a person.
Positive thinking will let you do everything better than negative thinking will.
What you get by achieving your goals is not as important as what you become by achieving your goals.