I don't know the whole quote...but it includes something like:
"as i am now, you too will be..." and "as you are now, so once was I..."

I believe it's a poem from a gravestone and I don't remember where I heard it. Can anyone help?

oops...sorry...I didn't mean to double post.

The church of Sta. Maria Novella, in Florence, contains a fresco by Masaccio, "The Trinity" (ca. 1427). Below the fresco is a skeleton in the wall, with the epitaph, "io fu gia quel che voi siete e quel chio son voi anco sarete" ("I was once that which you are, and what I am you also will be").

There may be an earlier source for the quote, of course. This is just the earliest I know of.

See Frederick Hartt, "Italian Renaissance Art," Third Edition, 1987, published by Harry N. Abrams. Pages 203-4.

We must learn to love life without ever trusting it. G.K. Chesterton

Where are we going? And why are we in this handbasket?

I see Viktoria has better information. This is what I found. I'll delete the other post.

It's on a lot of different gravestone markers, various versions and forms. I don't think it has an author associated with it.

"The original of this epitaph appeared in a European monastery. It has been oft copied and rewritten. The author seems to find it in nearly every cemetery he has visited. Readers of the Epitaph Browser send it to me more than any other inscription, each believing the sentiment unique. This page consists of many variations upon a theme"
http://www.alsirat.com/epitaphs/passing.html

The Rose is red: Ye grass is green
The days are past which I have seen
As you are now so once was I but
as I am now so shall be ye
Be prepare for death and follow me.

Kind frineds beware as you pass by,
As you are now so once was I;
As I am now so you must be.
Prepare, therefore to follow me.
~on the headstone of Catherine, wife of Lawrence Hartnett, died 02/26/1883, aged 56 years, Roman Catholic Cemetery of Holmdel, New Jersey
http://www.atlanticmedical.net/genealogy/holmdelcatholic.htm

O' come and see this lonely place
All tho you cannot see my face
This land of darkness & of night
Here I'm concealed from your sight.
Remember me as you draw nigh,
As you are now, so once was I;
As I am now, so you must be
Prepare for death & follow me.
http://www.gendex.com/users/pthree/ss%20cemetery.html

Stranger stop and cast an eye,
as you are now, so once was I.
As I am now, so you will be.
Prepare for death and follow me."
http://blacksheep.rootsweb.com/2000peep.html

YOU LIVING FRIENDS, AS YOU PASS BY,
AS YOU ARE HERE NOW SO ONCE WAS I
AS I AM NOW, AS YOU MUST BE,
PREPARE FOR DEATH AND FOLLOW ME.
http://freepages.genealogy.rootsweb.com/~langolier/hooper.html

...as one gravestone noted: As I am now, you shall be too!
http://www.heritageinterp.com/gravesto.htm

Herb speaks to us; by his great ego we're led;
Let not your heart become reanimated.
I'm in the grave, and soon you shall be too;
I'm in the grave, and soon you shall be too.
http://www.herbertwarmstrong.com/gycg/herbspeakstous.htm

"Real generosity toward the future lies in giving all to the present."~Albert Camus.

Ah, yes! You have been of great help! Thank you!!

I know where this comes from!
Okay so there's this story about a woman named Sarah Cottington. She had three children, two of whom died from tuberculosis. Her husband was at work one day when she noticed her third baby coughing. She didn't want this baby to have tuberculosis as well, so she hitched up the carriage and rode off to the doctor. However, when crossing train tracks, the buggy was hit by an oncoming train. Sarah woke up in a hospital to doctors saying things like "We can't believe you lived through that!" But all that Sarah could say was, "Where's my baby?" The doctors told her that there was no baby found at the scene of the accident. Sarah eventually went mad, and died in an asylum. Her ghost is said to roam the ground of White Pines Dude Ranch, (the camp the train tracks happen to run through) although in the five times I've been there, I haven't seen any ghost. Anyway, there's a cemetary next to the ranch, and on her gravestone, it reads:
Remember me as you pass by
As you are now, so once was I.
As I am now, you soon will be.
Prepare for death, and think of me.
I think this is what you are looking for, Breakaway77. The ranch is in Oregon, Illinois, and you won't believe how excited I got once I saw that someone was wondering where that quote came from!

All ye readers who now pass by,
As you are now, so once was I,
As I am now, so must you be,
Prepare for death and follow me.

Gravestone in Cheshire, MA

I believe this is the orginal.

Effie Jean Robinson

1897-1922

Come blooming youths,

as you pass by ,

And on these lines do cast an eye.

As you are now, so once was I;

As I am now, so must you be;

Prepare for death and follow me.

Upon which someone scribbled:

To follow you

I am not content,

How do I know

Which way you went.