Can't
It’s confusing to me how casually people are willing to throw around the word "can't". That word carries more weight for me than for most people I think. Whenever someone tells me I "can't" do something, I invariably find they actually mean one of three things. Starting from most common to least common:
What you want to do is beyond my abilities, therefore, it must be beyond yours as well.
What you want to do has consequences that I find to be an effective deterrent.
What you want to do is not possible according to the laws of the universe as I understand them.
It’s not that I can’t, it’s that you won’t.