Many say that they can be super-confident in some areas of their life and not in others. Such as acting on stage being no problem but then struggling to say anything at a drinks party. Some are able to make calls all day long and handle client meetings without a concern but ask them to present to a group and they suffer sleepless nights.
What is self-confidence?
Your self-confidence relates to how you view yourself and how you perceive others view you. It is how much you believe in yourself and how self-assured you feel.
What is not self-confidence?
It's not arrogance and risk-taking that can harm you or others. It's not bragging, aggression or over-compensating, especially when trying to keep up with others.
How to improve your self-confidence
Clothes & Posture: This doesn't mean throwing out your current wardrobe and starting again. A confident person can walk tall in rags so whatever you're wearing stand upright and shoulders back. A slouching, slow dawdle does not say confidence. An upright stance with a steady pace, looking straight ahead and not down on the ground, says, "I am at ease with myself."

Compliments: Stop the negativity and start offering and accepting compliments. When a friend or colleague tells you your hair looks great then be gracious and say thank you and don't try to back that up with the fact you wanted a different style but the hairdresser didn't listen. Don't dwell on weaknesses but focus on gratitude instead. Say thank you when it's deserved.
Ask questions: We don't live in isolation so when you meet someone new, or catch up with an old friend, ask them questions. Not an interrogation but show them you're interested which, of course, means listening too. The person who asks the questions in a conversation usually controls it so aim to be that person as often as possible.
More than words: Only 7% of communication is words, the rest is voice tone and body language. Even if you say the right things when you meet someone new if you were looking over their shoulder or at the floor and your voice lacked enthusiasm then why should they want to talk to you? Look at the person you're speaking to and know that you often can't remember the first words when you met a new person but you usually can remember how the meeting made you feel.
Try new things: As we get older it can be harder to welcome change but challenge yourself to try something new whether it's a hobby or travel outside of your comfort zone. Just because your last birthday was a landmark age that doesn't mean you can't try a bungee jump over the Zambezi River. Or join a book club with your neighbours. Trying new things doesn't mean stretching yourself beyond your physical capabilities but just trying something you've not done before.
There are many more ways to improve your self-confidence but these ideas should get you realising it's not such a great leap. Do share any other ideas that have worked for you.