Too much of sth ?

[hookeba]

I frequently come across those terms like "too much of a good thing", "too much of a rush", "too much of an apology" and so on.
What does each of them mean ? What is the general meaning of the structure: "too much of + a noun" ?

I would be obliged if you could give a detailed explanation.

[Tdol]

It means 'excessive'- chocolate is nice, but five boxes is too much of a good thing. If I say I was in too much of a rush, it means that I didn't have time to stop and do something because of the hurry I was in.