What does 'keep your cool' mean?

Read the excerpt below and answer the question. nice town, y'know what i mean? nobody very remarkable ever come out of it, s'far as we know. the earliest tombstones in the cemetery up there on the mountain say 1670-1680-they're grovers and cartwrights and gibbses and herseys-same names as are around here now. in at least one hundred words, discuss the significance of the stage manager's narration in our town. analyze the text in terms of its tone, word choice, and meaning. what purpose does this narration serve in the play?