Qi: The name of the Zhou Dynasty vassal was in Qixian County, Henan Province. There was a man in Qi who was afraid that the sky would fall. Metaphor is unnecessary or unfounded worry and anxiety.

Complain/complain about other people in heaven and on earth-blame everyone and everything except yourself.

Heaven: destiny, destiny; You: Resentment, blame. It refers to complaining and blaming others blindly when encountering setbacks or problems.

Much ado about nothing: asking for trouble. Nothing, just making trouble for yourself.

this means

Don't worry too much about things you don't have to worry about, don't blame others, and don't make trouble for yourself.