Have you ever changed a delusional belief?

Dude..
People can believe all sorts of things.
The great gift that Western civilization got from Aristotle is a method of proving your beliefs have some reasonable chance of being coincident with reality.
A delusion should be changed as soon as possible. It is not healthy to cling to delusional thoughts.
But the answer to your question is yes.
My delusional belief was in Santa Claus.
The truth is, when it comes to Santa, I wish I had never heard of Aristotle. I loved that delusion!

Sure. I gave up religion, for one thing. I’d say the belief simply wore itself out. It wasn’t by anything I particularly did; it was more like when you say “This shirt has had it—one more laundry and it will just fall apart.” And you put it in the ragbag.

If you know it’s delusional, why do you still cling onto it?

I have to agree with @josie . Mine was Santa Clause too. I believed in him until I was 11. And only then it was because it was shoved in my face. I accidentally found a present before Christmas that was for me from “Santa”. And yes, it was accidental. I never looked for presents, I loved surprises.

A belief is one thing and knowing is another. The latter requires evidence.

@RedDeerGuy1 , We are all traveling through time, at the rate of one second per second. Your delusion is that you can travel backward through time. As delusions go, it is pretty harmless. Unless you start taking actions based on knowledge that you supposedly acquired on your time journeys, I don’t see any reason to let go of your delusion. If it makes your life more interesting then keep on believing.

Like many others, I let go of the God delusion. I was relatively young when I became an atheist. My family was not particularly religious and I had a close friend who was also an atheist, so the transition was not particularly difficult. Like @Jeruba , it was not a sudden occurrence, more of a realization that I could no longer believe in God.

I once believed that chiropractic medicine helped my leg injury, even though I had seen and read scientific journals that say chiropractic medicine has no basis in science

Examine your belief closely and honestly to see how it matches up with the evidence. Examine also why you are holding on to this belief, is it for purely emotional reasons? Don’t try to destroy your belief, just look closely at the pillars that support it. If you find they are rotten the belief may collapse of itself.

I once was pro-colonial.

Of course. I once believed everyone was inherently good.