The best way to improve self-control is to see and understand why you lose control. The willpower instinct looks at willpower from scientific point of view and provides stories and experiences from his days teaching at Stanford and performing willpower experiments there. Kelly also looks at willpower from a evolutionary point of view so we can have better context, and he describes how Willpower is an evolved mental instinct that initially promoted healthy group dynamics in tribes. A good perspective on willpower, is that it is like a muscle, so it can be strengthened but it can also be exhausted. Willpower failures can often be traces back to the individual being in a low physical state, for example, sleep deprivation and low glucose levels can significantly hinder the use of will power. Willpower can be trained through the development of habits and exercising discipline, such as creating and or meeting deadlines. It was a nice overview on willpower, but I felt like I knew most of the concepts described, this will be helpful to thoughts unfamiliar with the area.
I have been working towards consciously cultivating discipline and willpower as I believe that is the most high-level thing I can do to have better control over the things within my realm of control in my life. I honestly think that with more discipline there is more personal freedom.