A thought went up my mind to-day
That I have had before,
But did not finish,--some way back,
I could not fix the year,

Nor where it went, nor why it came
The second time to me,
Nor definitely what it was,
Have I the art to say.

But somewhere in my soul, I know
I've met the thing before;
It just reminded me--'t was all--
And came my way no more.

Emily Dickinson

http://www.poemhunter.com/poem/a-thought-went-up-my-mind-to-day/