Habits are the "secret sauce" to help you become more confident. Nick Wignall talks about four in particular that can help you.
Accept your fear
Fear helps you detect dangerous situations, don't get rid of it. Don't run away from it. Also, some fear enables you to perform better; through the hormones, it helps release and the neurological improvement you get. If you try to avoid fear, you breed anxiety, which is the last thing you want.
Communicate your wants and needs
Confident people act according to their desires. E.g., they are Assertive. If you always put other people's wishes before your own, you're always going to feel unworthy. To become more assertive, set boundaries, say, "No" to what you don't want, and respectfully ask for what you do want.
Make decisions based on values
Not on feelings. This means not avoiding tasks or situations because they might feel uncomfortable. Instead, stick to your principles. Choose values over feelings. An example of this is to not watch another season of Game of Thrones but to write that blog post, review that report, or clean your kitchen.
Be compassionate with yourself
Often, low-self-confidence goes hand-in-hand with being highly judgmental with yourself. This especially emerges after 'mistakes.' E.g., "If I wasn't so nervous, I would have no problem giving that presentation. No wonder people don't ask me to do presentations." This negative self-talk is usually unrealistic AND makes you feel even worse. Which creates a negative spiral. Try to be more compassionate to yourself, like you may be to a small child who is struggling with their own fear and anxiety.