I've found pacing to be the biggest problem with self-learning of academic subjects.

Suppose we are learning from a textbook. The things we learn in each chapter are built upon in the subsequent chapters. If we go forward before we have a good enough understanding it can make it very hard to learn that next chapter.

On the other hand if we wait to go forward until we feel we really have mastered the material up to this point it can take a long time to move forward, and that doesn't even really gain you anything.

The best way to master something is to practice it. The textbook author knows this. The author writes each chapter under the assumption that you are OK with the material from the previous chapters but have not yet mastered that material. You now need things to practice that material on, and using it while learning the material of this chapter is perfect for that.

That point where you have gotten good enough with the present material that you can handle the next chapter is almost certainly going to be a point where you do not think you are ready.