Confidence could be a trigger – a means to an end. It could be an active choice – to look a customer in the eye and make an ambitious promise that you will keep later. To get a foot into the door. To fake it until you make it. To raise the stakes to motivate you to deliver later.
Alternatively, it could be a result of doing something well. To etch neural highways in the brain with repeated practice, to makes it an automatic action – like driving a car with one hand on the steering, or perfecting a craft like a stone sculptor does.
You could choose to treat confidence either as a choice or a consequence.