You are only learning at a good rate if you are feeling interested. If you are feeling confused, then the input may be too overwhelming for your ability to process it. Your current thinking method cannot organize the input material well enough. Many people keep reading when they are confused and only compound their confusion. Others think that they are stupid when they feel confused.
Confusion is a healthy part of everyone's natural learning and growth process.
Our confusion can be like a door. Opening the door and looking at what our confusion is about will create learning. Instead, if you feel confused, immediately stop reading . Ask yourself questions. Try to answer the questions.