A romantic partner should never use the word ‘can’t’ when talking to their loved one.
There are going to be times when you will wish your partner didn’t do a certain thing, like spending too much money on a pair of kicks or staying out until the early hours of the morning.
But telling him that he ‘can’t’ do something makes you look controlling and kind of like his parent and you don’t want that.
As much as you want to tell him that, don’t, as you really shouldn’t tell him what he can or cannot do. He is a grown-up and he should know how to make good, smart decisions himself.