RETICENT

quiet

reserved

reluctant to express thoughts and feelings

tempermentally disinclined to talk
SYN - untalkative

cool and formal in manner
SYN - restrained, unemotional
ANT - voluble

reluctant to draw attention to yourself
SYN - retiring, self-effacing

"After having opened himself up and been stomped all over, it was excusable that he would be so reticent."

"He really struggled to remain reticent as he was expected when he felt so strongly opposed to the proposal."

"Due to the unwelcoming atmosphere of his co-workers he was willfully reticent in conversation with them."