Reserved
Part of speech: verb
Definition: To keep back; to retain.
Part of speech: adjective
Definition: Slow to reveal emotion or opinions. Set aside for the use of a particular person or party.
Example sentence: Money motivates neither the best people, nor the best in people. It can move the body and influence the mind, but it cannot touch the heart or move the spirit; that is reserved for belief, principle, and morality.
Reticent
Part of speech: adjective
Definition: Keeping one's thoughts and opinions to oneself; reserved or restrained.