His face and body language. I am a lip reader and pretty good at the body language issue - and I have used the body language issue with a number of friends and I am always right.
I actually find Harry's facial movements are that of someone sad. But that's my opinion.
I think that Harry is of that age where he feels he's ready to settle down now, he's had good times I'm sure ( sown his wild oats ). But now he has met the right girl for him, I hope they have a long and happy marriage.