Coming from a personal experience, I know how important having a bond with mom or dad is to a child. I am very close to my mother; we can talk about anything and she will help me understand. However, this is not the same with every child. Being a teenager is hard, but being an adult is even more complicated, yet a teenager only knows how to be a teenager. Giving them the opportunity to grow and learn from their mistakes is what will help them become an adult. I'm sure all parents have said at least one of these to their kids "Enjoy life now that you have no responsibility yet" or "when I was your age I would never have..." and that is completely true. Parents are wise and know what to expect. Parents also need to know that teenagers are just not there yet.
When your son or daughter is crying because the relationship they had with someone they love(d) is over believe me when I say it hurts. That's probably the worst pain someone their age has had. All they want is the comfort of their parent(s). When you find out they are being sexually active, they do not want to be yelled at. They know the consequences and the amount of trouble they can be in but they will still do it; that is part of becoming an adult. The right thing to do, in my opinion, is not take them away from one another,but to teach them how to be safe. If you just separate them believe me when I tell you all they are going to want it more now than ever. However, if you teach them how to be safe and try to understand, then there should not be anything that is going to anger your child.
When your son or daughter is going through the stage of finding their sexuality and wants to ask questions, they should feel comfortable to do so. We live in a society where we are already being judged by strangers, the last thing a teen needs is to be judged within the four walls of their home. Learn to accept and appreciate, no one is forever. It may be a "stage" or it may be permanent, regardless it is, in fact, their feelings and shutting those down is shutting down their self-esteem. Without the acceptance of the parents, a son or daughter will never really be themselves.
Friends are a huge support and part of anyone's life, yet it will never be the same as the comfort of a parent that a kid wants and needs. It is much different, so when your kid has a game or wants to accomplish something, please help them through it. Go to their games, be their number one fan. If they want to apply to every college in the world sit next to them as they fill out applications. All teenagers need is that moral support. The assurance that they are being the best they can be. If they don't ask for help on their homework still offer it. Ask them how their day is going, get to know them deeper than a friend can. A kid wants their parent(s) there for them in any way possible. Even if they do not ask for it, no teenager is going to admit that they care about anything.
At the end of the day, the parent is the biggest support a teenager can ever have; a teenager is only an adult in progress.