Once you have let yourself go then it is very hard to get on your feet and start moving again. As time goes on and people get a bit older, then people just have less time. If you are 17-18 years old then finding time to exercise and keep yourself in shape is not hard but when you are 25+ then it´s a lot more difficult.
How to get in shape and stay in shape
The first step is always the most important and also the hardest. You have to step out of your comfort zone and for many people that is too much. Some are not sure if they will succeed, others are ashamed of their weight and some just can´t find the time to exercise.
The most important part of getting in shape and burning fat is not what type of exercise you do, how long your workout is or how many calories you burn, what really matters is that you enjoy what you are doing. Once you have taken the first steps and have some good results, then all of those factors get more important.
Some people worry so much that they do the wrong exercise or do the exercise the wrong way, that their menu is not perfect or what ever, so they can´t get anything done at all. The less you think the easier it is. People ten to over-analyze things, especially when you try to get in shape after a long period of slacking off.
If you want to get in shape and stay in shape then exercising has to become a part of your life forever. If you don´t enjoy exercising then it is impossible to stay in shape. And a great way to find motivation is to collect data from your workouts. Write down what type of exercise you were doing, how long was your workout, how many calories you burned, what was your pulse, what was your body fat percentage etc. That way you will always have some personal records to go after.