Encouraging a stressed friend

Heyhey
My ex and still have something, but he is unsure about his feelings and future. However, he has much stress right now because of his exams. I told him he can first concentrade on that and afterwards we'll see what'll happen. We didn't see each other for some weeks, rarely talked and had no contact in the past 4 days. I know he has this way with dealing stress. I thaught about leaving a funny and encouraging message. Something that is not too cheesy. Do you have any ideas?