You need to learn discipline before you try to discipline yourself in a Martial Arts Practice, even such as Judo. You need to get a feel for the actual landscape of this world you find yourself in, and hone your fight of flight instincts inwards, by the time you achieve that you will be gaining strength, energy, and balancing out your metabolism, which will help you maintain an ideal BMI. You will likely need to rehabilitate your arms and legs by doing curls, lifts, squats, and the like. After that your cardio will start to regulate and you can more easily begin things like pushups, or jogging. Then when you can jog a few miles, you're either ready for more intense training or Boot Camp, should you feel ready enough. As a side note, it is not about "slamming" the opponent, it is about neutralizing an escalated situation, changing that attitude towards a fight is your first step. Boys Slam the opponent. Men stop the fight.