Your side project is easy to skip when you've been in meetings all day, are tired and hungry, and have to figure out what's for dinner. That's why many successful people put in an hour or so on their personal projects before they officially start their days.
A history teacher at the University of Chicago told Vanderkam that she spent the hours between 6 and 9 working on a book about the religious politics of West Africa. She was able to read journal articles and write several pages before dealing with her teaching responsibilities.
By carving out the time in the morning to write, and making it a habit, she could follow through.
She's not in bad company. According to the Telegraph, Ludwig Beethoven, John Milton, Kurt Vonnegut, Maya Angelou, and Victor Hugo all tackled their creative projects in the morning.