This might sound silly but instead of a new year resolution my friends and I choose a word. A few years ago I was feeling similar to you so I chose the word confident. I wrote that word all over, changed one of my passwords (it no longer is that), repeated it often. And strangely enough after a couple of months I started feeling more confident. This was both at work and in my personal life. I said it so much I started to believe it. It really helped.