That's pretty much a "saying." You'll find many variations on that theme.
You never know how much you love someone until they are gone.
Family is important and you never know how important until they are gone.
You never know how much you
Love that person,
Until they are gone.
I had to find out the hard way,
And I regret never getting to say Good- Bye.
http://www.netpoets.com/poems/death/0663001.htm
You never know what you have until you lose it,
Luckily for me I didn't have to lose it to find out,
For a love for these things are not known until they are gone,
Treasures in life are taken advantage of and not realized,
You say my life is so bad, but yet is it really?
Look around at what you do have
and you will see the good treasures in life,
just next time you feel down look at life a little harder.
For there is a friend inside of each and every living thing,
whether you see it or not.
http://www.texramp.net/~dbell/visitors/Carter.html
http://www.barriolife.com/TrueStories/shounte1971.shtml