I got through a few lectures by recognizing that I didn’t have the mathematical training/practice to finish up one video in one sitting. Often times I would need to scurry on over to have some basics explained to me on another site. I did one lecture over several days (weeks if I had to). I think most of the discipline comes from expectation management. Expect to get stuck and need a few moments or days or weeks to mull something over until it becomes more intuitive. Keep a list of things you do and don’t understand (a simple text file / paper is enough) and keep doing it for a few months if you have to and you’ll get there.