Of course it's going to be hard. It's going to require you to reverse decades of your lifestyle and eating habits. This is why so many people fail or rebound, because they stop making the changes or revert back to how they were. Real weight loss requires real change in your life. You can't just drop 40 pounds and then go back to how you were.
People are fat because they eat more food than their body can burn off. For example, Americans now are easily eating 600+ more calories on average in a day than Americans in the 70's were.
A sedentary lifestyle coupled with lack of exercise or fitness, in addition to highly processed and calorie heavy foods will make anyone fat. People are getting up, driving to work, hitting drive-thru for coffee and doughnuts, they take elevator up, sit at a desk, have lunch, finish work, drive home, order a pizza or takeout, eat and then sit on the sofa and watch television or play games, and then fall asleep and do it again. That's life for a lot of people, especially adults.
Any dietary change to a sedentary lifestyle will be difficult to keep up because you're going to start to feel angry or hungry if all you're doing is sitting on the sofa but eating salads and wondering why the weight isn't necessarily coming off so quick. You can't reverse years of fat/Weight gain in weeks or even months.