Sunday night anxiety is the worst. I know exactly what you mean by that! Its almost as if I feel better it just being Monday already and the week can get on with it, rather than waiting all Sunday in lingering fear for the week to start.
I have been trying to get to the bottom of my anxiety problems for years. Its a by product of fear for sure. I think Dox says it right that you need to accept yourself. After some research I'm trying to accept myself and stop trying to be perfect. What is security anyways? A feeling? Feelings are not finite, though, so maybe its not security you need to be looking for.