Make a list of the deeds you do in public
Make a list for those done in private
Check your life: are you showing off? Are you doing things for people or for Allah?
Another sign of showing off and arrogance is that you will avoid doing good things for fear that people will see you and think that you are showing off or for fear of arrogance. Try to find a balance people!!
p.S. I want to write a book soo bad. What should I write about?