"Your smile will give a positive countenance that will make people feel comfortable around you."

-Les Brown.

Even if you don’t want to smile and end up putting on a fake grin like a maniac, people will be more willing to approach you. They’ll be inclined to smile back and trust you, and you’ll feel that things will go easier as well. It’s infectious, and it’s an essential skill of customer service. You have to do it even if you feel like something’s going to be long and complicated and they’re going to straight up miserable at you. You might be able to reverse their thinking by giving them a positive experience, so long as you can react with sympathy to any bad news that they care to impart. Be careful if you’ve got bad breath or wonky teeth though, unless you want to scare them away. Sometimes it’s the eye contact that has it. And sometimes you just want them to leave you alone and approach someone else.