What if you tried to remove yourself as a factor?
I'd figure that focusing solely on your opponent would give you a stronger understanding of how they function. If you knew everything they were going to do, would you even need to know yourself? 

It does seem like it'd lead to a more advisory role. 

You need to know yourself, or you cant respond adequately. Your actions will be based on improvisations and luck.

Not sure how this quote works if you remove yourself as a factor.

An advisory role seems appropriate under such circumstances.

Good said:
Every loss is a lesson, but so is every victory, if you pay attention, its just a little slower at teaching you, but less bitter.

What's learned from your own victories really? I'd just see it as a means of padding one's own confidence. 

It is very rare a victory works exactly as planned. Even when you have non rigid plans, you still have a plan, expectations. And you should always try to improve, so every victory should be better then the last: aka differently executed. And when you execute your victory, you can observe if what you thought will happen is as you thought and if it is not, you can note these differences and analyse them. This analysis will lead to corrections or sometimes entirely new things.

But never sacrifice a victory over knowledge or experimentation, unless its an irrelevant battle. Sometimes the real victory is knowledge (when it is an irrelevant to the entire war battle).