I know its sounds kind of corny (in the Singapore context) but this simple gesture helps keep me grounded daily and remind me of what is really important.
I am sure at some point in their lives, they would see that it helped make them more self assured, confident and, it might do wonders in building a close realtionship with them. Of course, I guess there are a thousand other things we, as parents to teenagers could do e.g. not being judgemental, taking an interest in their interests etc but telling them that you love them is start. I would like to think that if we really believe this, everything might fall into place. 🙂