It's the number one advice that you hear over and over again for performers and public speakers. Be confident: just be confident and it'll all be fine. And in some sense it's true. If you're confident and self-assured, your voice will carry further, you'll be more convincing, and you'll feel happier with the results.
But I take issue with this advice - it assumes that everything wrong with a speaker's performance is to do with internal factors. For instance, how high their self-esteem is, or how much they believe what they say. Again, it might be true that a low self-esteem can make performance harder - but asking someone to correct their whole self-image just to be able to speak in front of people seems like disproportionately hard work. It is a colossal effort, spent over years, to iron out enough psychological hang-ups to finally become confident.
So if dealing with the internal factors is too time-consuming, what can we do instead? Deal with the externals. Instead of being more confident, be more engaging. Think about how you hold yourself while performing - keep your head up and eyes focused outwards. Increase the power and deepen the timbre of your voice. Slow yourself down so that you match the rhythm of the room. Always think about engaging with people - bringing them in to your world.
That single word has the power to change your whole perspective. Confidence is showing off. Engagement is honest. Confidence is dependant on self-esteem. Engagement is neutral and consistent. Confidence is about the speaker. Engagement is about the audience.
And guess what - if you're engaging enough, and people are paying attention to you, your self-esteem will skyrocket. Once you start getting the results you're looking for, you'll find engagement and happiness easier and easier to come by.