The second principle we follow is: What you do to get healthy is what you need to do to stay healthy.
This simply means that if you choose a paleo, keto, Mediterranean, vegan, intermittent fasting diet, you will have to stick to it long term in order to retain your progress.
This is where most people screw up, they pick a restrictive diet, have some short term success, then return to their old way of eating and regain all that weight. Life is a lot longer and more complicated than a simple 12 week challenge. Even in a year, 12 weeks is only a quarter of the year, you have the next 40 weeks to undo all that hard work. This is why you see people do 12 week challenges every year without it ever seeming to stick.
You need to come to terms with how you relate to food (see my last post), and how you best like to eat and exercise (more on that later).
Look to establish simple habits and routines, rather than follow fixed rules. For example a common thing people do in order to lose weight is skip breakfast. If you however have spent most of your life eating breakfast, you will probably go back to that habit in the future, thereby adding calories back into your diet without realising. So sticking to a pattern of breakfast every day and changing its contents is much more sustainable.