I was asked this question by one of my team the other day, and I thought what an awesome question. I had learnt things that day but looking back and reflecting on them helps me cement them in my mind.
What did you learn today?
Did you learn anything? Even something small? If you didn't are you developing as a leader? What would happen if you asked yourself every day? What would happen if you asked different people you work with what they learnt every now and then?
Ask the question!