10 things that build genuine confidence

The ability to respond to adversity and setbacks and overcome them

You need expertise in a domain or a set of interrelated domains to feel confident. The more years of deliberate mastery the better you will be.

To feel grounded enough, you need various life experiences in different jobs, environments, and people. A person with years of spectrum of experiences and mental agility can often trump someone doing the same job for ten years. 

The older you get the more holistic view you will have on life. You realize that life is not insurmountable and that you handle many solutions with the right resources and expertise.

You know your boundaries and your values. You can say No to people. You take less crap from the world and are winning to pushback.

You get better at reading people. Know how to deal with conflict and negotiate. Learning out to deal with people that create drama. Be charismatic.

Learning to be non-reactive. Don't take people's bait when they try to provoke you or get all maudlin. Act as if you knew this was exactly going to happen.

There is a strong mind-body connection, and unless your body is in shape, your mind and, ultimately, your confidence will never be optimal.

Mindfulness is valuable in pausing an option or action. People tend to act on their impulses if they are roused to anger or emotion. Meditation helps you mediate that response.

You need to know yourself before you can hope to understand others. Not only how people act but anticipating how you will act about another individual.