I get stuck when I don't understand what I'm doing, especially WHY I'm doing it. Plus, there are many situations in which schools teach you things and don't provide enough guidance. They tell you what to do and how to do it, but when you think in a different way and misinterpret, you're suddenly on your own...
MOTIVATION-LEVEL: ZERO.

It's a normal reaction if you think about it. Schools generally use one template and force it on you. Most adapt and get by in their own way, but there are also lots of people who get really stressed out, lose motivation and in the end don't want to do, or are interesting in anything any more.
There's such a great pressure to perform and 'fit in with society', that teaching has lost its 'art' aspect. It's not something anyone can do, it's an art.
Remember back in school when everyone used to have one or two favourite teachers? Ones that actually got your attention and taught you new things without effort from your part? THAT's teaching.
Anyway...
I'm not trying to say school is bad and all teachers are incompetent fools (though many are), I just feel like there is a personal, social, human, inspired, whatever-you-want-to-call-it touch missing in today's education.
Once in a while it pops up, but it's fleeting, which is sad.
Just look at the whole school-culture, the high-schoolers especially. It's cool to not like school, it's cool to have bad grades, it's cool to not give a fuck. Just like wearing braces became cool all of a sudden. If everyone feels the same way, it becomes accepted.
Something's wrong...