Confidence is a prized treasure, and unwavering confidence is a once-in-a-lifetime treasure.
To be confident in yourself is to understand your flaws and accept them as it is, learning from them and knowing that surely, you will grow through them.
Ruby is confident in herself and in the Gods she serves. They are the greatest, no doubt about that.
She is and always has been confident in the might displayed by the Gods. Evident of that is her getting stronger after she unwaveringly prayed to the Gods for a miracle.
So what then is the problem?
As precious as confidence is, there is one element that works in contrast to its effect, Doubt.
To have confidence is to be one hundred be certain about yourself. All that can be overturned by an anomaly, a doubt not measuring less than 0.000000.
That is how powerful doubt is.