From my experience so far, tracking the dollars has been the single most important money changing habit and has made the biggest financial impact on our monthly spending. I'm not just talking about periodically glancing at your account on your mobile app. I'm talking about writing every single transaction down and categorizing it. While there are various apps (like Mint) that can handle this data for you, I've tried them and they never impacted my spending like actually writing it all down on paper.