Personal Experience
People talk about how there could be different levels of reality. There might be different dimensions. I really haven't been able to grasp this concept yet, but I now see what people are talking about.
I have been having random seizures that started my freshmen year of high school. During lunch one day, I started to feel weird. I warned by friend, but it was a different kind of weird. I realized I was having a deja vu moment. I thought I knew what everyone was going to say. I was freaked out by the feeling, so I was trying to see if I could change what I thought would happen. However, whatever I added to the conversation ended up being what I remembered happening. It made me feel like once fate is decided, it can't change.
I am now 19 and I have still been having deja vu moments once in a while. More recently, it seems like what I know should or did happen before, is changed. For example, I was sitting in my living room. The show on the TV and the way my cat walked across the room made me expect my mom to walk in from the garage. She didn't. It is weird because it is like I can imagine exactly what it would look like and be like. It feels like it happened before. I don't know. My mind has been a bit weird lately.
I have had deja vu moments since I was around 12 or 13 years of age I think. It just keeps getting more interesting and makes me think that different dimensions are possible.