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]
(..) Cause you have no teeth, you have no balls, kid. Look, I am stuck here. Why don't you find something useful for me to do. Unlike you, I am not useless. And I maintain my own property. These swamp rats, on the other hand, you just can help it. How long do I have you for? Toad, how long? (..)2008 Gran Torino
(..) taking it a easier? And some other thing, Dad. You really should get rid of the coffin nails. We were thinking about the house. You know, when Mom?s gone, it?s got to be a lot to maintain around here. Let alone clean. And you are here all alone ... Yeah, you know, there?s these great places (..)2008 Gran Torino