Whats the hardest topic to write about?

I find that an interesting question. To each writer its different. When it comes to erotic writing this is a critical point. If you write about a topic that bothers, bores, or humiliates you then its not a topic you should be writing. So I got to thinking, what topic is hardest for me? I can't write m/m homosexual stories. Not that I find anything wrong with them, or homosexuality in general, I just know nothing of the topic. I wouldn't know where to being. Besides, that doesn't "do it for me" so the work would suffer. Write what you know, as the saying goes. So if anyone is reading this I'd like to hear what the hardest topic is for you.

-Shadow Mandoll