I once knew a financially-independent 30 year-old brown belt in Brazilian Jiu-Jitsu.
He didn't work because he had to. He worked because he liked leading teams into places no man had gone before.
"Every time I face an opponent on the mat, I'll execute a technique that's meant as a test for my opponent.
When I execute my first test technique, their gut-reaction will tell me whether they're a White Belt (Beginner), Purple Belt (Intermediate), or Black Belt (Advanced).
Let's say the person's initial reaction tells me they're a Purple Belt. My next move will be to find out if they're a Purple Belt that's closer to a Black Belt, or a Purple Belt that's closer to a White Belt.
From there, each and every reaction they make tells me more and more about their level as a fighter. Now, sometimes when you have a very large white belt, it takes a bit of time to beat them because they have so much weight and energy on their side...but not for long. I simply let them shake out all of their energy...
...and at the moment they gasp for air - exhausted - that's when I strike.