Summarize the following:
If you want to look positive, work on smiling. While you shouldn't smile too much, as this can come off as fake, offering a smile to friends and co-workers can make you look happy despite negative circumstances.  Smiling may also lift your mood. If your smile more, this may actually encourage happy feelings in your brain.  It can be hard to make yourself smile if you don't feel like it. Try doing something like thinking of something funny. You can even reread a funny text or look up something funny on your phone if you're really struggling to smile. You want to be aware of the messages your body language sends to others. If you appear physically withdrawn, others may think you're sad. In order to hide sadness, work on maintaining relaxed, pleasant body language.  Keep your arms opened and your palms relaxed. Avoid crossing your legs. Try to keep them parallel, or even stretched apart slightly. Try to maintain eye contact when talking to someone. Watch your language. Your sadness may show up in subtle ways, so try to be pleasant in conversation. Try to use happier vocabulary in casual interactions and day-to-day conversation.  Try to use positive words. If someone, for examples, asks you how you're doing, say something like, "Great" instead of more neutral terms like "Fine" or "Okay." Be sure to watch the tone of your voice as well. With the wrong tone, even happy words can sound like they carry sad meanings. Vary your pitch slightly, as a monotone voice can indicate sadness. Many times, people who are sad withdraw from others or even take things out on them. If you want to hide the fact you're sad, refrain from doing this. Work on being pleasant around others. This can help you seem happier.  Smile at others, listen to what they have to say, and offer positive affirmations instead of criticisms. For example, "That's a really interesting story. Thanks for sharing." In addition to not criticizing others, do not criticize yourself. If you're sad, you may be tempted to tear yourself down. However, this will only show your sadness. Try not to let a negative inner monologue slip into conversation. You can't prevent yourself from feeling sadness. In fact, it can be detrimental to avoid negative feelings. However, you can calm yourself down and taper your reactions by focusing on your breath. When you're in a situation where you begin to feel emotional, slow down and pay attention to your breathing. While this won't make negative feelings go away, it can prevent you from showing your emotions externally.  If you feel sadness building, close your eyes for a moment. Tune in to your breathing. Focus on the natural rhythm of your breath. If you feel like you're breathing too fast, try to slow your breathing slightly and breathe in from a deeper place.

Summary:
Smile. Maintain a relaxed body language. Use positive words. Be pleasant towards others. Focus on your breath in moments of sadness.