what topics?

As I mentioned yesterday that I will write something in English every day to improve the language, a question is what content or topics to write? Everything I experienced in that day? It seems too big and difficult.

The best way should be: choose a topic or a thing I'm familiar with, think about it in English and write it down, continue the action for a week (or two) and then the next topic. All the things I have thought and written are my opinions or perspectives on the topics. It will be helpful when I talk to someone about one of these particular topics, at least there is something to say. This is an excellent preparation of "纸上谈兵" before opening mouth without any real English environment, furthermore, most mistakes can be avoided first on paper.