This letter wishes a friend good luck on a specific endeavor.
1234, Main Street
Boston, MA 02123
07 April, 2005
<Recipient Address Goes Here>
This is just a quick note to let you know that I'm thinking of you. I know that the <project> you're working on right now is proving to be very time consuming and you are probably feeling a little stressed out. Nevertheless, once it's finished, and you've done your usual superb job, think how proud you'll feel to have accomplished so much.
So, good luck to you as you complete this daunting task. I'll keep you in my thoughts and look forward to hearing from you when you have a free moment.
encl: <List of enclosed items goes here>