There is a profound truth about life that only you know. You've seen it inscribed on the walls of every room you've ever been in; etched into the faces of all the wretched souls you come across, as they squirm uncomfortably in the glaring sunlight of the horrible truth -- even if they don't know it -- seeking in vain to hide their attempts to escape.
Everything reinforces this truth. The way the wind bends the trees, the way the tide swallows the beaches, the way the moon hangs in a quiet Summer sky, haplessly, like it's beginning to think the string that holds it there is never going to snap, and it'll never have the pleasure of reuniting violently with the Earth.
You are deeply, intrinsically aware of the common thread that weaves its way around and between every thing you know. If you could successfully articulate it, if you could convey what you know to anyone else, you could create a bond between you and your audience so strong that nothing could possibly sever it.
But it eludes communication. Words are dull and clumsy, ultimately useless for describing your truth. Even ideas lack the resolution to zero in on it, because the more time you spend thinking about what you know, the less sure of it you become. The truth is like a message scribbled in an alien language on a fragile slip of paper, rolled up, locked up in a bottle, and tossed into the sea forever.
You are the bottle, the carrier. Inside you is an insight so powerful that it could instantaneously transform the world, if anyone were to ever read it. The sea is life: tumultuous, unpredictable, and able to whisk you to and fro at its will. But it cannot touch the message.
At the end of your journey, when you wash up in some distant shore, who will be there to find what you have carried there? Whoever it is, and whatever the message means to them, they probably won't be another bottle like you. Because bottles can't read.