I've seen a lot of these slogans and never got what they really mean.
Most Helpful Guy
KEEP CALM AND CARRY ON ?
it's a famous british worldwar II propaganda poster , to kind of ignore the war and keep on living their lives like they were before the war. The Nazi's should not be given the power to change the british lifestyle.
nowadays it's just retro , and I guess it stands for having a relaxed view on life , and not worrying to much8