Even if you don't feel at all confident, you can behave as if you are. Once you start acting confident, you'll begin to believe in yourself.
Let's say you've started doing freelance photography on the weekends, and you've got your first few paying gigs. Your clients don't need to know that you're new to this. They don't need to hear about how nervous you are. If you behave like a professional, they'll see you as one – and you'll start to see yourself through their eyes.
Figure out one way in which you could act confident,starting right now.
not at all 一点也不
I can't cook at all.我一点也不会做饭。
believe in sb相信某人
I am not going to believe in you anymore.我再也不会相信你了。