It's your choice to go deeper into it. The more you pay attention to this stuff, the more of it you see. But, a lot of people have no interest in that, because it's SO FUCKING WEIRD.
The only way I can describe deja-vu/past life stuff is like this: it feels like an overload of nostalgia. Instead of being like, "wow, that's my favorite game from my childhood" it's like "this is something I love beyond description that I have no conscious memory of whatsoever".
It feels like your memories are slipping through you like some kind of warm, but almost cold... silk? Like clothing you've worn before in the past is phasing through you.
IMO the bad stuff is people who try to predict the future for their own personal benefit. If it happens naturally to you, there's probably a reason for it. If it feels REALLY, off, though, it's something being force, and that's very bad.
I've had a ton of dreams about this... like, old, several story (3-5 I think), red brick building in the woods, kind of tucked away so you have to walk to it. I think it would be a government building. All I can remember about being inside it is this suffocating feeling like I'm being watched at all times, and that the paper I was handling was much more important than my life to me.
I'm researching the concept of families reincarnating into each other, and am trying to research my family line to figure out where I really came from.