Do you think it's more important for mid-career PMMs to double-down on their strengths, or shore up their weaknesses? Can you share why, and an example of how you've done so?

This is a great question and one that is definitely unique to the individual. I'd say for me, doubling down on my strengths while being aware of my weaknesses has been the move. We all have natural strengths that lead us to follow a certain path. Studying journalism and being a strong believer in words, empathy, curiosity, has allowed me to follow a certain trajectory that wouldn't have been possible if I focused on my weaknesses. However, as things evolve, certain weaknesses will essentially plateau your career. For example, I would consider myself an "expert" in PMM from an IC perspective, but knowing I wanted to break into exec leadership challenged how I delivered messages, held conviction, and said "no" versus being a people pleaser. Being self-aware of what subtleties you need to change to crack a growth curve are essential to incremental changes. TL;DR to things can be true at once: you can double down on your strengths while improving your weaknesses.