I've long since lost count over the number of common advice not to follow, both concerning writing/art and life in general.
Don’t listen to those. Don’t try to do what you believe others may want you to do, what they expect of you. Don’t go mainstream! Don’t even go near it.
This is my «advice» to anyone that might be interested:
Write about whatever you want, do whatever you want to do, art-wise, human-wise, probe and analyze yourself in depth and identify what makes you thick, what is truly important to you. Make a serious attempt to not be tainted by cultural bias and imposed learning and free yourself from what is already there.
Do thy true will!
That’s all there is to it, really.