Yes, braces are a tool for making a person more confident. Confident people are more willing to take risks both in their personal life and in their professional life. Someone with confidence is eager to date or become an entrepreneur. Finding a person to love and a suitable profession are the cornerstones to a happy life.
Yes, people who wear braces are bound to be happier and more successful, because they have more confidence knowing that they have straight teeth. This can lead to better jobs and an easier time making friends. People who wear braces are also more likely to have come from wealthier families, which means they are like to have other advantages.
People that wore braces as a kid will more likely be happier and more successful than kids that did not wear braces and needed them because they help them to be more confident as an adult. If feeling confident about your looks and braces enable that confidence, then people will be more happy.
I do not believe people who wore braces are bound to be happier and more successful. Braces have no bearing on success what so ever. Some people simply don't need braces, that doesn't mean they'll for some reason be unhappy or unsuccessful in the future. It also doesn't guarantee their future success or happiness. These two things simply are not linked.
People who got braces at a young age were shy and tried to stay out of the limelight to keep from getting teased. They tended to place a hand over their mouth when they spoke. After being shy and trying to stay hidden for 5 or 6 years I imagine it would be hard to turn into an aggressive, goal oriented individual.