How the heck to get back on track after slipping from a diet or exercise program?  Good news! Don't panic just read this first. After it, I allow you to panic...if you will still want to, but i doubt that. Let's do a little bit of mental exercise and here is how. 

First thing's first. What is the situation? Are you lazy and just don't want to train? Or got sick, injured, went on vacation or grandma's place? ...whatever may be the reason, we just slip off the training and “eating right track”. We get somewhat out of shape, put on some fat. We get depressed over this and just don't seem to find the necessary motivation to start all over again. We feel a failure. We have the feeling we are never going to make it, to have our dream body. So, we might as well don't even try again? Or?  Give up or not to give up? We don't know what to eat, how to start training again...what the heck with everything?! 
First. Calm down. When you are freaked out nothing is going to change or get easier. Take a deep breath and just understand the fact that we all get off the track sometimes. We just do. Everybody. Not just you. But you, and me, my friends, your friends, their friend's friends. Pop icons and stars slip up too. Everybody. It's a normal phenomenon. It doesn't make you a biological freak, it just makes you human. You hate it. I know. I hate it too, but I am content with the fact. It's just a variable that you have to include in your way of thinking about fitness and life in general. Life doesn't always go the way you would like it to. “You have to control your life, your eating, your behavior” ...and what else? You have to control everything... but do you? Or better asked: can you?  The answer may be yes, because sometimes life is easier and you can. But sometimes bad things happen, you get stressed out or whatever the reason and you fail. 
But please make a difference between failing and being a failure. Failing  means you failed once, twice or 102 times. Being a failure means that you don't try anymore. There is a huge difference between the two. You failed, but you are no means a failure. So, as fat as you have become, or as out of shape as you have become by not training and eating junk, you still have the potential to come out as the winner. Winners are those who just don't give a shit if they fail or not. They continue. And there is one thing that is a guarantee: trying will lead to winning. It may take 2587 tries or more. But who cares? Do you think that there is somewhere written how many times a human being can fail till he or she gets to be called a failure? No. There is no such thing. No such paragraph in any holy book or general law. The failing-quantity differs from person to person because we do live different lives. Some of us have easier existence, some others have much harder times. We don't start life equally. Some of us are born princes, some of us in middle-class families and some in very poor families. It is the same with our physical characteristics. Some of us are genetically more blessed than others. Why deny the fact? For example, I have genetically a big ass. I have since my adolescence. I accumulate fat there and it is damn hard and necessitates very strict diet to shred the fat in that area. I am like that. There are women with narrow hips from mother nature. They don't have to kill themselves to shred anything there. So, for me to have the same result as these women, have to work 110 times harder. And still, in the end, I will just look like the other one, which had that effortless. Is that fair? Is that right? No. Do we like it? No. But, can we change it? No. So we just start not to give a shit about others. This is the key to success. You know how you look like. Fine. You know what you want. You start to work for it. You don't give a shit about the immediate result because you are clever and you know that there isn't such thing as quick and easy. Otherwise, everybody would go around looking like fitness models. But the majority of people don't. Why? Because it is hard. Like yourself. Like your big ass, jiggly belly, because it only shows how strong you are, that even with that you still didn't give up. 
What is success? Success is relative. Today you didn't eat half of pizza for dinner but a salad with some lean meat? That is a success. Are you always a little hungry during the day? That is success. It means you burned some fat. Don't you see it? Of course. Cause you can't measure it with your eyes. Change starts at the cell level. And cells are pretty damn small as you know. Change happens. Imagine yourself like a big truck full of sand. When you take out 5 milligrams of sand, nobody would notice it. But think like this. If you start to take out 5 milligrams of sand each day of it, you can actually move tons after some time. Don't freak out because you see only the huge truck. Don't care about the truck. Care about your 5 milligrams of sand. Sometimes it's good to look far. Like when you are driving a car. But with the car you are moving very fast with. Think about the highway. You have big speed on the highway. So you look straight and far. But what if you are driving on a forest road, full of bumps. You look also at close range in order to avoid hitting the bottom of your car with some stones, for example. 
With natural body modification, you are never ever on the highway. You are on the forest road. So enjoy the birds singing, the smell of flowers and drive slowly and safely. Delete the failures of the past from your mind. You are starting now and that's it. Focus on what you are doing in the present, don't give a shit about your past or what might or might not happen in the future. These two don't even exist. Think about it. Past and future don't exist. One doesn't exist anymore, the other doesn't exist yet. Only the present, and you are doing something in the present. So, there actually isn't any damn problem, is it?