He began to write his thoughts and observations concerning the day's events [...] It helped him better understand everything he had seen and done over the course of the day.
The advantage of writing from experience is that it often provides you with details that you would never think of yourself, no matter how rich your imagination. And specificity in description is something every writer should strive for.
If you want to be a professional writer then you need to write consistently. Inspiration strikes about once every blue moon which, for me, is once every two and a half to three months, which is when I'll get really and truly inspired about something.
I find inspiration in many places. Sometimes music gives me the kernel of a story. Sometimes it's dissatisfaction with the plot of a movie or a book that gets me thinking. Sometimes it's love of a movie or book.
Just writing a lot doesn't necessarily make you a better writer. You have to hear yourself as a writer, and the best way to do that is to read your writing out loud.
There is much you can learn from books and scrolls. These books are my friends, my companions. They make me laugh and cry and find meaning in life.