“Mountain and sea” means that it is bad to do the same thing over and over again. You may have to repeat something once, but it should not be done a third time.
When you try something on an opponent, if it does not work the first time, you will not get any benefit out of rushing to do it again. Change your tactics abruptly, doing something completely different. If that still does not work, then try something else.
Thus the science of martial arts involves the presence of mind to act as the sea when the enemy is like a mountain, and act as a mountain when the enemy is like a sea. This requires careful reflection.
The above is from the Book of Five Rings. It is so important not be stagnant, to always improve and change your tactics, to try new methods, etc.
How many times have we seen that people expect a good result but does the same thing over and over and over again without any changes and improvements?
You can’t expect good or better results if you just stick to what you are doing now. At best, you can only achieve what you are achieving now.
To move forward, identify what you need to do differently and do it. Only then there will be a glimmer of hope for improvement.
Applicable to all aspects of our life, not just on martial arts or Go.