There are two main things going on with teen emotions that make them more of a nuisance. First of all - WHEN and WHY are they triggered? Your brain kind of decides when to trigger an emotion by following rules or beliefs about life, or seasons where something is particularly important. So anything that might clash with a rule or belief, or relate in any way to something your brain thinks is important right now will trigger an emotion.
So, let’s say that you step out into the road and a bus is coming. That clashes with your rule of ‘staying alive’ (we all have that one). So your brain triggers anxiety and you gasp, leap out of the way and avoid disaster.
Or - what if you REALLY like someone. I mean - REALLY like them, hope they like you, have serious romance plans, get it? And you’re in the dining hall or something at school or college and someone says something and it SOUNDS like their voice. Think heart rate RACING, cold sweat, attention GRABBED - you’ve guessed it, that’s another emotion your brain used there.