He 'kept/maintained his cool' [=he didn't get angry or upset] even though it was clear that he was being unfairly treated.
He was struggling to 'maintain his cool/composure'. [=he was struggling not to become angry or upset]
They barely had enough food to 'maintain life'. [=to make it possible for life to exist or continue]
(..) lost his head. Mercenaries all know the jambo, Amahl. Base, we're looking at a lot of Russian SA-s. Tell him to maintain eyes on the truck as long as he can. We're gonna find his stash and we're gonna level it with a Hellfire. (..)2016 13 Hours