Why do parents of teenagers have to live through hell?

Good morning to you all. I hope you have lots of fun stuff planned for the weekend or nothing at all so that you can just relax. I am posing a question today as once more, after surviving several years of stress, heartache, and struggles with my oldest son..who is now doing well I must say I must now repeat the same crap with his brother who is old enough to know better and who you think would have learned after watching everything his brother has gone through..what the hell is wrong with some of the members of this generation? Why are they so non motivated, disrespectful, and determined to be on the fast train to self destruction? For years I was in the mindset that all was due to the fact I had been a single parent and due to the life that that entails I took the blame and almost let it ruin my existance and goodness knows there is no freaking parenting instruction manual...we do what we think is decent job and heaven help us we all make mistakes along the way..but in this case there are 2 parents, life at home could not be easier or better and yet here we go again. Except this time I am stronger, have a wonderful helpmate, and even though I do not have a great church I can go to my faith is strong..made it a point to start a prayer and gratitude journal this morning to help through all of this mess..I realize that teenagers do not have it easy in these times but why must some of them make such crap choices?? Especially when they have every opportunity and option wide open to them? I just do not understand. Hopefully through my daily conversations with God I will find the peace and strength 1 day at a time until this also passes. As we all know it will, God will never lay more on us than what we can handle this I know, have lived, and can testify to 250%.
At anyrate, the show must go on and that includes taking care of myself mentally and physically so onto the treadmill I go..and then off to purchase healthy food items. 
Have a wonderful Saturday..Bis dann.