When someone is always brooding and in a bad mood, is it correct if I tell him " hey, laugh more, cheer up more." I've never heard of anyone say cheer up more, but if you can say laugh more, then can you also say cheer up more?
Laughing is a discrete action; saying you should do it more is essentially saying you should do it more often. This may include laughing now, but you're probably not giving the person an instruction to laugh at this very moment.
Cheering up is a change of state of mind that should be done once. Usually it's because the person is in a bad mood now.
It's not wrong to say someone should "cheer up more often"; maybe they're in a bad mood frequently. But it means something a little bit different than "cheer up".