Question

“What he could do he did.” How does this statement relate to our lives?

I think what the teacher meant is, "How does that statement relate to <I>your</I> life?" This is something you need to answer for yourself. I cannot relate it to your life.

You might be able to relate to it better if you changed the sentence to the first person — "What <I>I</I> could do, <I>I</I> did." What would that mean in terms of your life?

I hope this helps. "What I could do, I did." Thanks for asking.