I’m torn between two reactions:
On the one hand I want to say: ‘If you can’t put it clearly in words, you only have the illusion of having it clearly in your mind.”
But on the other hand I want to say: ‘You are right! – This is exactly what it is like to do philosophy: to struggle to say what seems impossible to say. In philosophy there is no saying things as a matter-of-course.’ (The hardness to say certain things as part of their grammar.)