As to harmony, I rather like to think of harmony as the following definition from Webster’s Dictionary:
1. The just adaptation of parts to each other, in any system or combination of things, or in things intended to form a connected whole; such an agreement between the different parts of a design or composition as to produce unity of effect; as, the harmony of the universe. [1913 Webster]
So, when I think of being in harmony with all things or being in harmony with this life, I think of it like that. Basically, being in “agreement” or to use the vernacular, “being cool with” the way things are. Not necessarily happy, because some of life is sad, but understanding that and being in harmony with the sad as well as the glad.