"It's all part of Life's Rich Tapestry"
The concept that everything has a place in the big ol' experience that we call life.
Good and bad, happy and sad, yin and yang - it just wouldn't be the same without both positive and negative aspects. Clearly it refers to the fabric tapestry, where many different coloured threads and designs go to make up the whole.
Sidenote: I was in the States recently and I used this phrase (which is widely known in the UK) in conversation with a friend of mine, and I was greeted with a blank look, followed by a smile and praise for inventing such a good metaphor.
I guess it just isn't widely used in the US.. There is, however, a 1986 album by R.E.M. called Life's Rich Pageant, so maybe this is the standard alternative over the pond.