Few things make a person feel so small and inept as when facing questions of suffering in the world.
First, there's the sheer breadth of the problem. No matter who you are or how carefully you've planned your life, suffering is going to hit you. Human life is tragically fragile and subject to forces well outside our ability to manage.
Second, there's the inscrutability of the issue. It's one thing to sit in a philosophy class and discuss suffering in a detached, academic manner, but in the real world, if you've ever been pierced by pain or grief, and you slow down long enough to acknowledge the "why" questions burning within you, you know the impossibility of finding a firm answer to grab a hold of. Our net of meaning is far too small. And if you've ever sat alongside someone who's suffering, you know the difficulty of finding apt words for the circumstance—in fact, it's often best to provide nothing more than your physical presence and a listening ear, rather attempting a pithy answer for your friend's pain.