Painful poems come from the same place that all moving writing comes from, deep emotion.
If you think about your own experiences, you will know that both great pleasure and great pain have the ability to tap into this emotion.
Not only are these feelings great, but they are also remembered.
I think the emotions pointed to here can be stronger and more deeply felt at a young age.
As Anne Lamott encourages, write about your childhood.
We Are Seven is one of my favorite poems.
Ann Sexton once remarked in an interview, when asked why she wrote such dark and painful poems, that pain engraves a deeper memory. Pain engraves a deeper memory. Think of a time in your own life when you have experienced a sudden shock, a betrayal, terrible news. Perhaps you remember the weather, the quality of the breeze, a half-full ashtray, a scratch on the wooden floor, the moth-eaten sweater you were wearing, the siren in the distance. Pain carves details into us, yes. I would wager, though, that great joy does as well. Strong emotion, Virginia Woolf said, must leave its trace. Start writing, grow still and quiet, press toward that strong emotion and you will discover it anew.
-Dani Shapiro, Still Writing