Origin: This phrase possibly originates in posters used during World War II in Britain that said ‘Keep Calm And Carry On’. Many variations of the original phrase have been created since that time.
Meaning: This saying has a bipartite meaning. Firstly, it means that we should stay calm, and thus, implicitly not get over emotional or worried. Secondly, it means that we should work hard, i.e. put a lot of effort into what we are doing.
Implicitly, these two meanings are linked. The saying suggests that ‘keeping calm helps us to work hard, and working hard helps us to stay calm’.