If you've never made an ATC here's some information about them:
ATCs are small works of art that can be traded with other artists. They can be fun to make when you don't have much time or space. They are also useful as little reminders of messages you wish to carry with you, perhaps in your handbag, backpack or in the car. They are also nice to give to others as little random acts of kindness.
-info. taken from: http://athp2014.ning.com/Workshops/art-swaps/gratitude-wisdom