This is a great way to use new year's to make a spiritual impact. Ask students to think over their past year and write a letter to themselves. Give them some spiritual questions to get them started:
Then ask them to place the letter in an envelope, seal it, and address it to themselves. Take the letters up and stick them in a drawer for several months. Sometime around may or June when you are rummaging through your desk and see the letters, mail them.
I also will do this at the end of a retreat with questions like what did you hear God say, what is something you don't ever want to forget, etc.