This term is already used to describe the cycle of human life in general. When used in urban slang the emphasis of the phrase is featured on the word GRAVE. Grave = gravy as in, "it's all gravy" meaning it's all good. When adding the "cradle to the..." portion in the beginning is just further verbage to emphasize the eloquence of slang.
This term came about when the movie Cradle 2 The Grave (starring DMX, Jet Li) had played ads on TV for it's release. Rapper Jedd Rizzun Michrophone Magician of San Jose, CA had coined the term and is used in that area as well as other parts of northern california.
Used in a response for an apology:
"Yo, ay man, damn... I didn't have your back last night, I was tore up!"
"Oh it's all cradle to the grave man.. I handled my own with those breezies"
Used in response to an embarrassing mishap:
"Haha!! You done spilled that drank all over your kicks.. haha!"
"It's all cradle to the grave... I ain't stressin'"
A 2Pac/Thug Life song off of the Thug Life: Volume 1 CD that came out in 1994. This has nothing to do with the movie "Cradle 2 the Grave".
From tha Cradle to the Grave, life ain't never been easy
Living in the ghetto.