When people get older, they understand that adolescents are still learning a lot about social behavior. TV teen shows such as, "iCarly" are hits because they present fictional teens in a way that real teens wish they could be.
Teens have a great many situations arise that they have never faced before and are unprepared for. They must learn by trial and error how to handle them and the errors are painful.
They are also unaccustomed to their (sometimes extreme) biological drives, they pick up bad habits easily, peer pressure is strong and embarrassment is deep and frequent. They make a lot of mistakes and must learn as they go.
If you try to overlook the many bad/foolish/embarrassing things they do, others will find it easier to do the same for you.
As an adult you will still have peer pressure, embarrassment etc. but with more experience handling them, those things will occur less frequently and not affect you as deeply.
The good news is that after high school, no one much remembers or cares what went on there. Their lives are then filled with all new things and having matured some they have long dismissed those blunders and headaches.