Confidence can occur in degrees. For example, we could have a little confidence, some confidence, a lot of confidence or a whole lot of confidence. You have it or you don't. If you believe you have a little certainty then you don't. This state either exists or it doesn't.
Certainty is always solution focused.
It rises above anxiety, fear, hurt or whatever and strives for solutions. In the sense that certainty exists where skill and confidence intersect we would have to say that certainty is more than the sum of it's parts. As you practice the things identified earlier in this article you will become more and more skilled in dealing with, and using, anger. Your relationship will become stronger and stronger as you and your partner's confidence increase. Anger will stop being scary and start being resourceful.