Understand that you and your son are different people with different personalities, sometimes they clash - ESPECIALLY when teenagers are involved. Remember when he was a toddler and he was probably beginning to test his boundaries? You would say "Don't sit in that puddle" but he didn't see anything wrong with it and wondered what would happen, so he did.
This happens again now as he starts embarking on a new point in life. There's nothing wrong with you, you are just looking out for your baby. Is there another way you can approach this with him? If he's not responding to yelling what else can you try?

What's the worst thing that would happen if you didn't walk him through these things? I'm not saying they aren't important, but put the responsibility on him, at 13, he can handle it. Tell him, "you are getting older so I think it's time that you start making responsible choices. I'm not going to tell you to when to brush your teeth, but if you don't you may get cavities and you will have to use your allowance to help pay fort he filling". Maybe he'll go to school smelly and his friends won't hang out with him that day. That might upset him enough to show him why you are asking him to do it.