For a man notable for his unwavering conviction, it's a bit of historical irony that Oliver Cromwell gave us one of the most quoted reference points for intellectual humility. But then again, he was counseling someone else to think they might be wrong, not suggesting that he might be. So, in character after all.
Our minds are wired to display decisive confidence in the opinions we hold and want to defend. This has evolutionary origins and advantages. To survive and thrive, our instincts drive us to win fights, defeat opponents, and leave no doubt. Whether predator or prey, nature doesn't tend to reward nuance, self-questioning, and careful processing of information.
So it runs counter to thousands of years of conditioning to develop the habit at the core of constructive dialogue and "good disagreements" - allowing for at least the possibility, however remote it might be, that we might actually have it wrong. Or at the very least, that there is information we don't have and differing viewpoints that we haven't fully considered.
So how do we actually overcome our evolutionary wiring to be better at disagreeing? As with any effort to transform bad habits into good ones, it's a matter of conscious effort, repetition, discipline, and practice.
Own it: you're wrong about stuff. We all are. We have been before, we will be again. Remind yourself of this before you hurtle headlong into disagreements.
Assume good faith. This is especially difficult in the anonymous digital arenas where so much 21st century disagreement takes place, but it is crucial that we begin by assuming that whoever disagrees with us has arrived at their opinion for defensible reasons. (Obviously, there will be occasional exceptions to this, paid political operatives, self-interest, etc).
Know the best version of an opposing argument. Get in the mental practice of knowing the reasoning behind what the other side thinks and how it got there. Defeat your impulse to reduce the opposing argument to a caricature.
Be self-aware: take a minute to call yourself out. Whether it's the reflex to disregard your parents' opinions about your life, or the impulse to dunk on anonymous combatants in an online debate, we all have ingrained impulses in discussion. Know yours, and have enough detachment to laugh at yourself sometimes.
Ask, restate, listen. Whether it's your mom, an old friend, an anonymous flamethrower in an online forum, or an annoying colleague at work, develop the habit of restating your understanding of their opinion, then listening closely to see if you have it right.
As I write this, I grimace at how routinely I don't practice everything I preach above. Which speaks to the fact that none of this is easy. I also grimace at the fact that I ate half of a pizza at 9 PM a couple of nights ago, thereby negating the positive effects of a 90 minute workout earlier in the day. Developing healthier habits and maintaining them is never easy.
But when we do, the outcomes speak for themselves.