The road to perdition...

To love oneself as much as Narcissus loved himself is not a healthy thing to do. Self esteem is very important, since you need to take care of yourself for not to harm your body. Also to have self respect, and be able to trust yourself, and be confident and stand high, with your head front. But some people have way to much of this, to the point were it is annoying and can get them into trouble for show-offs and obnoxious attitudes. Everything in excess is bad. 

Probably it wont be drastic enough to lead us into dying. But still the story is a good example of being "Narcissist"...The metaphor could be that it is possible to drown in your own beauty, like those beauty queens that for so much make up and surgeries, they turn out to be ugly, after this. Or because of taking care of the outside, you turn a bad person on the inside. All of this could be. Beauty is not all, the inside, the person you are and believe in, is more important than how you look (though I think there has to be a balance!). 

What would happen if beauty is lost? I don't really know, but I do know that if you are a good person, you won't let anybody down, even if you are not physically gifted...

in difference with Narcissus, Theseus was a true and brave hero, having sleighed the minotaur with his own hands to save his people. This is something pure. His strength, in this case, was what mattered. 

The greed, the ambition to have more, to be better is also bad in excess as it happened to Daedalus' son, Icarus, he just had learned to fly, so he wanted more, more power, higher, and without listening to advice, as we sometimes do, we then fall hard to the ground, observing how we rushed with excitement into something we had little experience on. this happens to us all the time.“Icarus, my son, I charge you to keep at a moderate height, for if you fly too low the damp will clog your wings, and if too high the heat will melt them. Keep near me and you will be safe.” Sometimes it takes more than one fall for us to learn, but sometimes, we don't have a second chance...