I've observed the following happening a couple of times to me now.

I wake up in the morning from a dream; in my dream, would be somebody I had reasons to 'hate' in the past, but I have been consciously trying in recent times to question my reasons to 'hate' them. That person would do something in the dream they hadn't even remotely done in real life to me, leaving me feeling really bad, and reinforcing all the 'hate' I had for them. When I'm awake from the dream, all I'm primarily left with is a very strong feeling of hate.

Now if I don't question why I felt so towards them, right after waking up (that is by recollecting the dream and realising its absurdity, which is an effortful exercise), I might've carried that reinforced feeling/reinforced belief and gone about with my day, which I suspect I did almost every time in the past.

This is not unlike the F.R.I.E.N.D.S episode in which Phoebe is mad at Ross and she can't remember why, and in the end she attributes it to a dream she had.

That really concerns me and I've decided to be more vigilant to largely unexplained feelings of 'hate' or similar feeling/belief.