There was something extremely wrong here. It wasn't just the flight failure that made Kon seem remarkably different -- it was his behavior too. He seemed terribly unsure of himself, yet simultaneously all too willing to head out and put himself in harms way, knowing all too well that doing so would prove to be a dangerous task. Not in the noble, justifiable sort of way either -- it wasn't as though Kon was declaring that he was going out to fight some terrible being that needed to be stopped, one that could potentially fatally harm him -- he was talking about walking, metaphorically (because the comparison would seem silly in Kon's case otherwise) into a bullet.
It was almost suicidal and Clark found that he was very far from okay with the idea of his younger friend behaving that way. Whatever had triggered the issues in his flight seemed to be linked with his change in emotional stance and Clark, standing beside Kon now, was all too determined to see to it that he found a way to cure both of those things. Emotions first. Flight later.
"Kryptonite is fatal to us," Clark pointed out sternly, "you could walk right into a room of it without any support to back you and end up in a lot of pain. Or worse. What I don't understand is your indifference to that logic. Logic that you know is more than justified."