Why is it that I can only seem to write when I'm upset?

i write poetry, but i can only seem to write (especially lately) when something negative happens to me. why is it that i can’t channel any positive emotions into my writing? this may be one of those questions that only i can answer, or it may be difficult to answer without reading my writing or knowing me well, but i was wondering if anyone had any general thoughts as to why it’s so hard for me to write about positive things.