Write about anything you would like to write about because we mostly like what we desire and this is all driven by emotion and in the creative writing process emotion sets everything in motion. Have you ever wondered how most people became writers? Most of these people were facing overwhelming emotions whether they were positive or negative these emotions were so powerful they needed an outlet and writing was the answer. The power of these emotions overcame the resistance so easily that their brains had no choice but to come up with masterpieces and when it was all done and dusted  these people gazed at what they have done then they appreciated and then curiosity found it's way, "am I capable of doing this again?" then the journey began.
Since we live in an era ruled by critical thinking, we don't have to wait for a tragedy.
write about the unordinary and  train your mind to flow naturally without any disturbances. this is the route most people that you call  "geniuses" have taken.