One of the first personal development books I have ever read was The Power of Habit by Charles Duhigg. This book introduced me to the genre of popular psychology, one that is often characterized by interesting and useful psychology combined with storytelling. This book looked at the science behind habits and how to change them.
After finishing the book, I was excited to apply some of the theory on habit change that I learned. However, I found it difficult to make lasting changes to my habits in the way that I was expecting. I would try many times to change my habits with some levels of success, but not in the way I was expecting after having read The Power of Habit.
In recent years however, it started to click for some habits. I made significant changes in how I used Facebook, and how I used YouTube - both habits that I had tried to change for many years.
A big lesson that I learned through this process was that constant experimentation is necessary. Although I was not successful in the beginning, I was still gaining knowledge about myself and how I responded to certain changes. All of that was necessary in order to eventually arrive at the right strategies to make significant changes in my habits.
Although understanding the theory behind how habits work and how to change them is important, you will most likely not succeed the first time you try changing a habit. Starting from an understanding of the theory, you have to experiment until you find something that works.