A lot of people who talk about language learning often stress the need for confidence when speaking. "Just be confident" — common advice. But pretty useless advice.
When someone is nervous, it generally doesn't help at all to tell them, "Don't be nervous." This only addresses the outermost expression of an internal sensation, rather than the cause of that sensation itself. Often, such advice can make the person more nervous; without knowing how to "just stop being nervous," the inability to stop the sensation of internal discomfort can create further discomfort.
We are all confident when it comes to speaking our native language. Why? Because we know it. We know it to the point where we don't have to think about it. Telling someone to "be confident" when speaking another language ignores the roots and causes of confidence. It's quite simple: when you know what you're doing, it's easy to be confident. When you don't, it's really hard to be confident. So, what's the solution?
Confidence is important when speaking another language, but it's just an expression of something more important: knowledge. Through correct training you can know that you are saying something correctly, and when you know you're doing something right, the confidence just comes naturally. Telling someone to "be confident" is like telling someone to "do it better" without explaining what "better" looks like or how to achieve it. By focusing on the roots and causes of actions rather than on their external expressions, the issue of confidence largely disappears.
Learn the language well. Confidence comes later.