If you want to have self discipline to do the things you know you need to do, then you need to know your “why”.
Your “why” is what drives you and stops you from getting lazy and giving in to temptation.
For example, if you weigh 500lbs and you want to lose all that extra weight, you will be presented with temptations to over eat, eat unhealthy foods, etc.
In those moments of temptation where you want to binge on 3 big Macs and 2 Oreo mcflurries, the only thing that can get you to resist the desire to over eat is to have your “why” deeply ingrained in your mind.
Your why in this situation is your ideal body. What feelings does having that ideal body evoke inside you?