When you think of moving on from something, the general idea that first comes to mind is that you're 100% over it and don't feel hurt, angry, upset, etc. over whatever happened.
Unfortunately, that just isn't how things go.
Moving on isn't all or nothing. Moving on is like a ball moving back and forth on a line between two extremes of "I'm as hurt as if XYZ just happened" and "I don't feel a thing about it anymore."
I've always thought of moving on in the "all or nothing" way. It's what was always implied when others spoke about it, because "moving on" is always assumed to mean you feel absolutely nothing anymore about the situation. Setting "100% over what happened" as the end goal is a tad extreme and may honestly not be accomplishable.
Moving on is an emotional and mental state.
Negative experiences mess with your emotions and your mental state. OF COURSE you're not going to be okay after something happens. OF COURSE, it takes time to move on from the experience.
Just like your emotions can get all over the place, moving on from a negative experience will find you all over the place. One day you'll feel fine and like everything's good, and the next you'll see something on social media that brings it all back. Ok, so it might be on the same day you're feeling good (re: it ALWAYS is, just to ruin a good day), but you get the point.
Moving on doesn't just mean "letting go." Moving on is also learning to accept and come to terms with what happened.
For example: I had a close friend in eighth grade who dumped me and left me in the dirt come high school. It took me many years to let go, and it was one of several negative experiences with former friends that messed with my trusting abilities.
Have I completely moved on? Mostly.
The event doesn't impact me emotionally like it used to. I can think about the experience and not feel the wave of emotional pain I used to feel. Just a few months ago, I saw this friend again and didn't feel the urge to rip her a new one like I once used to.
The point is, just because you've moved on from something doesn't mean you immediately can't feel anything about it anymore.
You are still allowed to be angry, upset, hurt, etc. Those feelings are VALID because you experienced something negative. If you didn't still feel some emotional tug when you're reminded of the negative experience in some way, I'd be a bit concerned.
Moving on doesn't mean not feeling anything anymore. It means you come to terms with/accept what happened as "this happened, it sucked, and there's nothing I can do about it now." It's not allowing those experiences to hold you back from doing things in the present and future.