A dig, an excavation...

"When you knew and taught me as a kid, did you think I was or would excessively focus/ed on just one thing?"

"Actualy, when you were that age, I thought you would never ever focus on anything at all!"

"Just joking! My real fear was that you would become so absorbed by/with ideas, that you'd never consider or move towards... practical matters."

Hmm.