When the soil is fertile, it can grow many types of crops. Crops which serve as food for people. In the same way a fertile mind cultivates some great ideas. But a wise mind does not overestimate its fertility. Wisdom tells it what to cultivate and what to give up.
Great thinkers have great ideas. But all ideas cannot be executed simultaneously. Ideation and execution are 2 different compartments. The thinker should not feel that just because he has thought something great, now he can execute. Execution is a separate department. The skills set are different.
Your mind can come up with some great thoughts. Focus allows you to choose only that which will lead to success, that which is dear to you. You need to choose your road. Only consistent effort on your chosen road will make a difference. Often it's not the road you choose that matters, it's the walk you take that makes the difference. You can't wander on every road. You have limited energy. A fertile mind can't grow everything.