Haste makes waste ie 'quickly doing things results in a poor ending'. Most of us by now know learning is a relatively slow process. It typically takes years to earn a Black Belt, it also takes years to finish schooling and years to earn a degree etc. If you're not patient enough then you are one of those persons who will get upset if they cannot see the grass grow. If you're patient enough you will eventually get results so you shouldn't despair when things don't seem to be working out for you on partciular days whether it be in the martial arts or at regular school. The 'grass will grow' as long as you put some work in! Sometimes, if you have high expectations then expect to see the frustration set in. Some people just need a little more time than others to get to the fnish line.
Learning is a like a sinewave. It has its ups and downs. There is no such thing as a perfect day, every day, but that does not mean you don't step out of your front door if the weather is a bit cool. The same goes when you have your bad days in training; nobody's an exception. Sometimes, learning may appear to be too slow because the other 'guy' is moving faster than you, giving you the perception that you're too slow. It's just that the other guy is moving faster than you.
'Slow' is not necessarily a bad thing; Hanshi Tino Ceberano has said it many times, "Slow to learn, hard to forget". That sounds like me; I'm actually better at the things that took me a little longer to learn.