The tips begin at a different place in each module. The advice moves along with the stages of the course.
Building your scientific knowledge base is like building a garden. As you make progress through the course, more comes under cultivation. The garden gets bigger. It's good to be making progress. However, there's a hazard if you only move forward and you don't tend what was planted last month. Those rows will begin to go fallow. After working in the new section of the garden, remember to devote time to weeding and watering what was put in last month and the month before. Every knowledge item needs to be visited every few weeks. Even if the visit is only a short skim, you need to show it to your brain again.