Mother was right
When I was young, my mother always use to give me a good size dose of cod liver oil whenever she thought I was not looking all that well.
She said no matter how it tasted the medicine was good for me, and that by taking it my health would improve.
To this day I truly dislike the taste of cod liver oil, but mother was right, taking my medicine when it was needed worked.
Today I see many student practicing in the dojo who could use a good dose of my mother's cod liver oil, because to me their basics and their kata do not look all that healthy. Yet class after class they still avoid taking the medicine that they need to get better.
You know what I mean.
A solid stance, correct placement of all blocks and punches, good posture, proper balance, timing, all those things that if taken to heart, and applied in the appropriate measure, would help make their basics, and their kata, look great.
However, in spite of constant reminders to improve the quality of their karate, and private lessons to remind them of what is needed, many students still fail to practice what they have been taught. As such their present level of understanding remains unaltered, and often their personal progress continues to be slower when compared to that of their classmates. 
The simple fact of the matter is that for these students the message is not sinking in.
Yet in spite of this fact, it is often these very same students who still feel they are ready to learn a new kata. A higher kata. All the while not realizing, or not willing to admit, that they are in fact still struggling with the very katas that they so often claim they "already know".
More often than not it is this supposition by the student that they "already know" all of the katas that they have previously been taught, that really is the crux of the problem. I imagine that from their prospective, since they can get from point "A" to point "B" in all of their katas, and they can get from the start of the embusen (pattern) to the final movement, they probably think there is nothing more that they need to focus on in that particular kata. So why not move on to the next one, after all what else can there possibly be left for them to learn - right?
The answer of course is a great deal. 
It is a fact that no matter how much you think you know, or how good you think you are, there is always a great deal more that you can learn when it comes to all aspects of karate. But that is especially true when it comes to kata.
The trouble is most student today do not have the patience to delve deeply enough into each of the katas that they already have been taught in order to find the answers that they are missing, let alone to try and figure out what questions they should be seeking the answers to.
I suppose having been brought up in a "fast food, fast cars, cell phone, computer driven, I want it now world" these students are simply in a rush to learn as many katas as they can.
The only problem with that is there is no fast way to learn a kata well.
Understanding any kata takes time.
It takes patience.
In fact it takes a lifetime.
In the end very few karate-ka will ever put in the years of effort that are really needed to understand what the words "I know this kata" truly mean.
So whose fault is that?
Their parents?
Their teachers at school?
Their Sensei's?
Or theirs?
In the end karate, like anything else, comes down to two things, "what do you want to know, and how well do you want to know it". Once you decide on the answer to those two questions then it is simply a matter of applying yourself to the task at hand until you finally get the job done.
For example, some people will put in the required effort to obtain a Bachelors Degree in a specific discipline. While still others will be willing to put in the extra time and energy to obtain a Masters Degree. Then you have those people who are willing to go the extra mile, and devote whatever time, and energy it takes to obtain a PHD and a Doctorate in that same discipline.
It is the same with karate.
Regardless of how much time and information the teacher provides them with, in the end the task of "learning" falls squarely on the students shoulders.
Not their parents.
Not their teachers at school.
Not on their Sensei's. 
Others can tell them what they need to know, and how to practice to become better, but, in the end it is up to the student themselves to take their medicine, and to apply the knowledge that they have been given in the proper manner.
That medicine of course is, effort and hard work.
A simple formula really, but one which so few students seem willing to swallow on a consistent basis.
A shame really, since the longer and harder a student practices the art of karate the more they will come to realize just how much there is still to learn, but so many students get frustrated and quit rather than simply putting in the effort needed to succeed.
That is why the saying, "for every one thousand students who start karate, only one will ever make it to black belt" is so true.
So the next time you think you "know your kata" ask your Sensei if you can get up and do it in front of the whole class.
And when you are finished the kata if you found a flaw in your stance, in your basics, in your timing, in your focus, in your balance, or in any other aspect of the kata, then think again before asking to be taught a new kata.
Chances are you will have just discovered that you still have some things to learn about the kata that you think you "already know".
If that is indeed the case then take my mothers advice, take your medicine, and take it in large doses.
You may find that the health of your karate improves to the point that your Sensei will notice. In which case he or she may just take it upon themselves to start teaching you the next kata in line.
As I have said before knowledge comes to those who seek it, however, knowledge only remains with those who apply what they know properly, and on a very, very regular basis.
Karate is just like boiling water,
if you do not keep the heat on,
your skills will cool very quickly.
Part the clouds - see the way.
"The objective of karate-do is to contribute to the evolution
of the human spirit through physical and mental training."
Sensei Peter Lindsay