I have worked with many people who don't even realise that this internal dialogue is there, they accept it as who they are, not ever questioning that self-belief. But here is some things we know about failure.
A good mantra for you would be something that speaks to your soul, that works with where you are now to help you get to where you want to be.
Today is one of those days. I have a cold, so meditating is hard because I can't breathe. My breath catches in my throat making me cough, and I feel so tired. It's times like this I often sit and think about all the things I could be doing, SHOULD be doing, and they go round and round my head and it makes me feel worse.
I was sinking into the spaces between my thoughts when a thought went by that aroused a flash of anger in me. The emotion was strong and I knew it was time to listen.
Negative feelings like sadness, depression, loneliness, trauma, hurt, anger and loss are useful and essential emotions. They tell us that something is wrong and it needs to be changed, or worked through. Loss of a loved one for instance cannot be changed but it can be worked through with the process of mourning.