I've found some poems that I think will be excellent for your purpose, but due to the fact that you're limited to writing only a few lines on the small gift card, you might want to use one stanza of a poem like this:http://nethugs.com/christian/every-sunrise/
I also like this one, by Helen Keller:
The best and most beautiful things in this world
cannot be seen or even heard,
but must be felt with the heart.
Here is another one about a 'New Day'--author unknown:
Each new day is a new beginning-
to learn more about ourselves
to care more about others,
to laugh more than we did,
to accomplish more than we thought we could,
and be more than we were before.
Occasionally in life
there are those moments of unutterable fulfillment
which cannot be completely explained
by those symbols called words.
Their meanings can only be articulated
by the inaudible language of the heart.
- Martin Luther King Jr.
A kind heart
Is a fountain of gladness
freshen into smiles.
- Washington Irving
Please let me know what you think of these, so far, and if any will be good for your purposes. You can see more here:http://www.thoughts-about-god.com/quotes/quotes-life.htm