I will try to keep this short as possible.
I started teaching as a 'head instructor' when I was a red belt. My original instructor/school owner had all but disappeared, which left me and another red belt teaching all the classes and taking care of the office stuff. With approval from our GM and the class contingent, I found the cheapest place to rent with enough space, relocated the school, and with a Lot of sweat equity from students and family, we started, with a slight name change. Things went very good from the beginning. As you can see, I did not start from scratch student-wise which was a huge benefit.
I was young in my 20's and had worked hard outside of class at my 'regular' job and also had/have a good-sized cattle operation. I had great credit and great backers/financiers. An opportunity came along to purchase the small strip mall the first school was located in, so I bought it. In a nutshell, it allowed me to operate the school with almost no overhead. Five years later, I did the same thing in another part of town and opened our 2nd school. I cannot overstate how many good things and opened doors fell my way in our early years. But to be very clear, it took a LOT of work.
That is a bit of explanation of how our schools got started out.
More to your question, I started out teaching out of necessity and discovered I am pretty darn good at it. In my early years of teaching/learning, I was extremely competitive. I had a crazy busy schedule with a very fulltime job, cattle operation, family, and teaching/owning a school. On top of all this, I had a four-year run of working out with a trainer 5 days/week, 4-5 hours/day to make an Olympic run. It was an insane schedule where I averaged about 4-5 hours sleep per day.
I still had a partner in the school (other original red belt) and he was good at the background office stuff and did a very good job of keeping things going and organized which helped tremendously while I was training.
I would say I absolutely fed off of teaching/training back then. No matter how tired I was from the rest of life, I always looked forward to classes. I have always been self-driven and quite competitive at Everything (my wife can attest). After my competitive days and after I had become quite seasoned in my original style (4th Dan if memory serves) I trained to green sash in Kung Fu, black belt in Shotokan, and 2nd instructor in Kali. I never have been 'tired' with my base style, but I knew there was more to martial arts than my base style, so I wanted to learn more. This also helped keep me engaged in teaching.
I hope I answered your question somewhere in there.