You cannot build confidence while repeatedly witnessing yourself surrender your own principles.

Confidence is not something you talk yourself into. It is a conclusion your mind reaches from watching your own behaviour, and you are always watching. Every time you fold on something you said mattered, you are gathering evidence against yourself, and no amount of encouragement will outweigh what you have personally seen you do.

Rather than working on how you feel, work on giving yourself something better to observe. Choose one principle you have been abandoning and hold it once this week, even in a small setting where the stakes are low. Confidence tends to arrive quietly afterwards, as a byproduct rather than a project.