Why should we smile and be happy around people? We might be really depressed people deep down inside, but it helps to have friends. Fact is, most people don't like being around someone who's such a downer. I lost many potential friends because of this, unfortunately. So why not put on a smile and a happy attitude when we're around others? You might not feel like it, but just try it. Smile more around your friends, crack some jokes. It might cheer you up and after some time, you may not even be able to stand your own depressing self when you're alone. Those friends will turn into a reason to be genuinely happy. So you may not feel happy when you're on your own, but you'll be much happier around your friends, and they'll love being around you. Who knows, eventually you won't be so alone anymore. None of that dark cloud, thanks.
I admit I don't know the secret to living a happy life, but it's a theory and a state of mind that I'm trying out for now.