[kevinh456]

"everything changes dramatically" - Practice each little bit one element at a time.

Posture is a great place to start. Just practice making sure that you keep a confident posture. Standing up straight. Shoulders back and relaxed. Head looking forward and alert. Focus on keeping your posture. A lot of how people read "confidence" is noticing these cues. It will become second nature if you practice.

Check out "power posing" also. Works for some people, doesn't work for others. Totally works for me.

For your voice, what is it doing? Probably going up higher? That's because your muscles in your neck are tightening up. Gotta keep them relaxed. I bet you'll find when you get your relaxed posture in place that your voice will change less also.