My understanding of the word 'chill' is that it is a mix of a 'state of mind' and also denonates a relaxed pace.
A synonym is "easy-going", that can mean not worrying about the future, not being sensible to any sort of pressure and also being friendly with others.
Assuming that 'working hard' can be done efficiently in a widespread range of industries planning and performing tasks in a very clever way, I don't see any reason for the two being incompatible.
Are these two concepts contradictory ?