When you find yourself, dragging yourself, kicking and screaming in the direction of a goal you know damn well is good for you, get excited, you are breaking an old habit that blocks your road to happiness. Focus on the glow of how the better results feel and push through. The new habit will prevail with less pain of discipline.
Why do I struggle is, as always, the wrong question. Like, why do bad things happen to good people? The question should always be what am I going to do about it? Always go to where people are helping because there you will find hope.