There are so many but this one comes to mind.

Watch your thoughts ,they become words,
watch your words they become actions,
watch your actions they become habits.
watch your habits they become character.
watch your character,it becomes your destiny.

I also like this one,
To handle yourself,use your head,
to handle others use your heart.

This one is a common one known by many, but i really like it.

Yesterday is history,
Tomorrow is a mystery,
Today is a gift,
That is why we call it the present.

I have a couple of cute cat ones too.Not exactly quotes but still i wanted to include them just the same.

Home is where the cat hair sticks to everything but the cat.

Cats are just children with fur.

Cats are like potato chips, you can't just have one (aint that the truth)