You can't quit!
A new student who has never been to a karate class yet comes back each week will learn how to punch, block and kick and the more they practise the better they will get. A student who has just achieved yellow belt will learn more advanced techniques - strikes, blocks and stances, and can begin learning how to spar. It even applies to a senior student who is learning a new kata. The key word which is common to all students is perseverance.
In other words, if you quit then you will not learn anything new and you will not improve.
At a class recently I gave the students a set of techniques to do and added that if they weren't sure what to do then they were to copy one of the senior grades. One student said the senior student can do it "because they are a brown belt". This student had it backwards! The senior student had a brown belt because they could do it, and if they couldn't then they would keep trying - persevering - until they could.
Improvement is 90% mental effort and only 10% physical effort. The physical effort is only the energy you use, the mental effort is keeping a good attitude and continually trying to improve. It is easy to come to class and just "go through the motions". It takes effort to push yourself to get better.
And no, you can't just do the mental part by itself!
- Mick Todd