This is the way we’ve told stories for thousands of years.
Here is a PDF based on the ideas presented by The London Script Consultancy, the people that organise the screenwriters group that I go to in London. It shows a line that represents how well the protagonist is doing. It starts with the line lower on the page. As the adventure starts, the protagonist does well – the line rises up the page. At the mid-point, the line falls down the page so that the protagonist is even worse off by the end of act 2. Luckily, due to the lessons learnt during the course of the story, the protagonist does well in act 3 and ends up in a better state than at the start.
I hope this will make a lot more sense when you download the PDF.
Another point is that each of the eight sequences also has the same structure within it, as does each scene. This is known as a fractal structure (the same pattern at different scales), but if you don’t want to bother with chaos theory, please don’t worry about fractals.