(krĭp′tə-nīt′) n. Slang Something that presents a particular threat to 'one that is otherwise powerful':
In this case YOU ARE THE ONE! You are the ONE that is powerful.
Superman had super powers, including the powers of flight, superhuman strength, x-ray vision, heat vision, cold breath, super-speed, enhanced hearing, and nigh-invulnerability (which means it is almost impossible to injure him in any serious way and yes I had to look that up).
Even with all that power he was "messablewith" by kryptonite, an alien mineral that has the property of depriving Superman of his powers.
Now for Superman Kryptonite was REAL, literally physically real.
I invite you to start to notice what YOUR kryptonite is.
What messes with you? What throws you off your game?
What messes with you may not have the same kind of reality as an alien mineral, it is likely more in the form of thoughts, beliefs, reasons, justifications, feelings etc. but the impact is pretty much the same.
When you start to be able to see what's messing with you, it begins to give you access to dismantling the seemingly SOLID nature of it so that you can develop the ability to go beyond your current limits.
Score some victories against your kryptonite this week and begin to develop the muscle of being UNMESSABLEWITH.