I know of two major ways to try to build up a sense of confidence.

One is to try to control for every possible outcome - to plan exhaustively, to eliminate every possible way things can go wrong, to avoid any potential mistakes or accidents, and to strive to ensure that everyone else involved makes the "right" decisions to follow the plan.

Planning is seductive, and it is often encouraged by the overculture we exist in. A really good plan can make us feel very confident. But planning is also extremely brittle, time-consuming, and tiring. It takes a lot of work; and when plans change, or something doesn't go according to plan... the blow to our confidence can be devastating.

The other way to build up confidence is basically the opposite of trying to plan or control anything.

Instead of focusing tremendous energy on trying to prevent anything from going wrong, we can gain confidence by knowing that no matter what happens, we will be able to respond effectively. Making mistakes isn't a problem; we just learn from them, adapt, and keep moving. Not getting the results we were hoping for isn't a problem - nor are the inevitable emotions of disappointment when such things happen.

We can acknowledge that we made an effort, learn what we can from the experience, and accept that some things simply are going to be out of our control. If nothing else, we can prove to ourselves that not getting what we hoped for won't break us.

In this mindset, the concept of "failure" becomes an illusion. Nothing can truly go wrong, because we can - and will - deal with anything that occurs, whether we are able to predict it or not. There's no need to anticipate the future, because we know we'll do just fine when we get there.

It can take a profoundly intense amount of work to develop this habit. It is especially difficult to learn to think - and live - this way, when we have a history of trauma and anxiety. But, speaking from personal experience, the change is worth it - and the rock-solid confidence that we gain from it is unmatched.