Something that's helped me understand processes is @jhull's advice to not think of time as linear, but to see the whole story happening at once. There's a lot of things going on in a story, but I can say to you, "Casablanca" and envelop all of it at once... and you know what I mean. What that story feels like all at once.
It's like the inner workings of clock. Looking at the individual parts, things are spinning, or ticking, or springing, or turning. Each of its parts going through its own unique process. But one can stand back from the device and simply see a wristwatch.
So with stories, I've found it helps to look at seemingly bizarre things like Past-ing in context to understand them. It's very hard to "get it" on a purely conceptual level. Watch films, pick them apart...
- In a History of Violence, Viggo has some pretty intense skeletons in his closet, and those things from the past are catching up to him.
- In Field of Dreams, the Past is showing up for everyone in the story.
- In Young Frankenstein, the history between Frederick and the Monster/Victor is the main force at play driving that relationship.
In all of these, we see the Players fac**ing** problems with things that deal with the past.
Honestly, the original Dramatica definition says it pretty well:
The past is not unchanging. Often we learn new things which change our understanding of what past events truly meant and create new appreciations of how things really fit together. A story that focuses on the Past may be much more than a documentation of what happened. Frequently it is a re-evaluation of the meaning of what has occurred that can lead to changing one's understanding of what is happening in the present or will eventually happen in the future.