Sounds like losing the 10 lbs did you some good...!! Congratulations...!!
But odds are that the next 10 lb loss won't get you the same time reduction unless 191 was quite a lot heavier than you should be. Most folks experience declining returns on their effort as they approach higher fitness/lower body fat levels.
I think that ordinary folks with ordinary resources should approach higher levels of performance with some caution. It's not easy to maintain an appropriate workout routine and an appropriate diet to lose weight and maximize fitness while dealing with the demands of having a life, a job, a family, etc. It's very easy to overdo... I know quite a few cyclists and runners who have over-trained and had to take significant time off to recover. A few have trained down to near-zero body fat and then continued to lose weight - losing muscle tissue instead of fat - especially when have lost weight quickly.
The most important thing folks like Lance Armstrong or Michael Phelps do is to pick the right parents. This gives them the perfect potential body structure, etc. for their sport. Then, they have the added advantage of professional coaching, professional equipment, professional dieticians, etc. to maximize achievement of their very high potential.
Just be careful as you continue toward excellence.