A phrase typically used to indicate that having too much of a "good thing" generally becomes a bad thing, and you're gonna have a bad time.
This applies to pretty much everything - even seemingly normal everyday habits - as well as more obvious examples like food, sex, drugs (especially alcohol), and, hell, even water.
All of them can be good, and they often are. But too much of any one of them will always lead to negative and painful consequences, some sooner than others. Especially if you're actively trying to ignore those consequences by continuing to over-use said "good thing" - all you're doing is just putting off that pain until later... because you're still gonna have to deal with it eventually. Somehow, someday, it's gonna bite you in the ass, and the longer you push it off, the harder it's gonna bite. Could be physically, mentally, emotionally, or even spiritually...
In fact, people are very frequently utterly destroyed by good things.
The difference between medicine and poison is always in the dosage.
There's really no such thing as "too much of a good thing," because once you start reaching levels of "too much"... then whatever you're doing, it ain't a "good thing" anymore.
A word that replaces very good or incredibly awesome.
The car turns much good.
That vacation was much good.
Tommy sister was much good for the cum suck this weekend.