Use the adjective restrained to describe something that's kept under control, such as strong emotion or even physical movement. If you're angry but you don't want it to show, you might speak in a restrained manner.
Restrained can describe someone or something that is physically immobilized or held back. For example, an angry crowd might have to be restrained by riot police. Or it can mean a different kind of holding back and describe something that is understated and discreet. Actresses who walk the red carpet often avoid attention-getting gowns in favor of more restrained outfits in times of war or national crisis.