if the subject of the change in my behavior comes up I want to be able to have a good answer. Something like, "I realized 3 weeks ago that my mindset and my actions weren't helping our situation so I decided to make a change and focus more on improving myself and focusing on the positive aspects of my life. I want to make this marriage work, but if I can't I still need to fix my own problems so that I can be a better man and father."
Whats wrong with just this? The rest sounds like youre trying to sell her on you.