I would suggest this is the wrong move, yes. Someone that lost a loved one doesn't want to forget them. They want to remember them. I wouldn't tell them to be calm or even to take heart. The important thing is simply to be with them in their pain. If they're crying, hug them. Above all, your presence, there, with them in their pain, even without saying anything, communicates a tremendous amount. Just love them and support them in their pain :)