It depends at least in part on how you conceptualise money. We’re not dealing with physical cash so there’s really no separating some of the money in your account that you got from a dividend from some other money in your account that you deposited yourself; they both are just contributions to your balance.
Personally I’ve always had that attitude even when it is physical cash. That £5 I got for my birthday when I was a kid was no different from any other £5 I had so I didn’t treat it any differently. It was just money that I had.
It’s your money regardless of the source so when you get a dividend think of it the same as any other money that you’ve deposited. Would you put further deposits into the company that paid the dividend or do you think your money would work better for you elsewhere?