Well, you can become aware of time flow to a much greater degree then we typically have. And then notice how things are shifting. Most people don't notice.

Most people do not pay attention to deja vu, and what information it relayed. The important stuff is the emotions that flooded across.

The emotions are what actually shift you onto another reel.

For the most part, deja vu is you looking at a different part of your reel.
If you do not like what you see/feel, you can use that to change your reel.