i teach english as a second language.  I have done so for years and in several countries.  I dont think that we should pick these words apart to decide what it means.  Look at the situations that native speakers use phrase.  what are they're feelings when they say it.  In my experience people say this to people they care about.  They want this person to be happy and enjoy their life.  maybe they feel they work too much.\nor, it is often the case that they want that person to go out that day.  when the reply is, " i cant, im busy" one often hears, "you work too hard".\nbut really, it is mostly said as a parting line....another way to say goodbye.  like take it easy