This quote is telling you to only write about topics which you feel genuinely passionate about and have firsthand knowledge or experience of. You should never try and write about something or someone just because you think you “have to” or it will make an interesting topic. When you write, make sure it comes from a place of love and enthusiasm, so that your writing is genuine, sincere and engaging. Writing should come naturally to you and be something that you do because you enjoy it. Writing purely to please your audiences or because you think it’s expected of you will likely result in less interesting and heartfelt pieces of writing.