The etymology of the word journal indicates clearly its greatest strength. First appearing in English between 1355-1356, it came into the language through the Anglo-French words jurnal or jurnale, meaning a day or a day’s work. It comes from the Latin diurnalis just like the word diurnal. (Chambers Dictionary of Etymology).
A journal is not a place where you draw or write only when you are inspired. A journal is a place where you draw or write every darn day!
It is a practice, it is a routine, it is a habit. It is the shear repetition that makes it so powerful, in an unromantic, uninspired, unstoppable, and self-reinforcing way. Journaling every day is like Bruce Lee doing pushups. You have to be focused on the pushups, not on showing off. Embrace the practice and enjoy the work and power and ability will come on their own.