Doubt in your ability to keep to this decision to save your own life is the same sort of critter as the craving itself - both are fighting for just another drink. To both of them I say FIE, aroint! Take off, eh?
I look at it like this. It is simply impossible for me to ever have a drink in my hand if I never doubt my ability to stay sober. It's the niggling maybes / whatifs that can erode my confidence and and my resolve along with it.
Overconfidence by definition is too much. Belief in self is never too much, that is what makes all change possible. Stick to your guns, SickOfThisCrap. Stick to your confidence in your ability to stay sober. Believe in yourself, you can do this! Onward!