1. What's the matter? 2. What's wrong? 3. Are you all right? 4. You look a bit down. (= a little sad) 5. Is there anything I can do to help? 6. Cheer up! / Chin up! 7. It's not so bad. 8. Everything will be OK. 9. Look on the bright side. (= consider the positive aspects) 10. It's not the end of the world. (this phrase is used when someone is upset about something small and trivial)