I think if you can do the former, the latter will follow. When you're out and about, remember that all those other people sit down to crap just like you do. And if that doesn't help, maybe try to have some fun with them.
Start with just a friendly "Hello," or "Hey." And make sure you try a little smile, too. If your attempts at being friendly don't quite work, get creative. Try greeting them in the queerest voice you can muster. Queer in this instance meaning stereotypical flaming homosexual, not queer like Gollum. If they look frightened, try giving them an "are you sh!tting me?" look. Feel free to laugh a bit, too. After all, you're not
that hideous! If they look like they might crap their pants, just ask them not to. "Please don't crap your pants. That's what that old lady did on Tuesday, and I really can't take any more."
But if you say anything to someone, try to say it with a smile on your face. And remember that you know a genuine smile (or a darn good fake one) by looking in the person's eyes. I know it can be hard when you feel terrible, but sometimes just letting go a bit and having a laugh can help brighten your day.
And if you get dirty/frightened looks after interacting with someone, at least it will be because of something you did and not who you are.