What to write in a "get well soon" card to someone dying with a terminal disease?

Gosh you poor thing - thats a really really hard thing to do. I really feel for you. Maybe you could start by saying thank you to the person for being a really good friend, and then write about some memories that you and they share, things that you've done etc and say what wonderful memories you'll always have - jeeze I don't know its so hard but I hope you find the perfect words. Good luck to you.