"I'm Happy Now"

When Ryan gets into trouble, we've been putting him in time out in his bedroom. He is told once he calms down that he is allowed to come out, but until he's happy he has to stay there. This is becoming slightly ineffective. He's decided that when we're taking him to his room he says "I'm happy now" and thinks that he'll not get sent to his room. He still has to go, and it breaks my heart to discipline him that way and when he says that it makes it really hard to resist.
He's been saying "I'm happy now" for other reasons too, which surprises me a little. He says "I'm getting tired, mammy" and I'll tell him he can go lay down and he'll start going, turn around and say "I'm happy now" to which I tell him he's not in trouble, but if he's tired he needs to lay down. He said it this morning while watching cartoons and I told him he could lay on the couch and rest. He looks at me and says "I'm happy now". I told him I knew he was happy, but he could still lay down for a bit. Needless to say he's chasing Mike around the house just now, so he must be "happy now" and not tired anymore.