Writing comes from YOU. This means that the better you understand yourself, the more likely it is that you'll develop a satisfying career.
A writing log helps you to get your mutterings, whining, and confusion down on the page. Sooner or later this will teach you about yourself: what you're enthused by, what scares you, when you need to push yourself, and when you're just plain tired.. Of course, you can also go into therapy, or get a coach, but a writing log's cheaper. :-)
I keep a log for each new project, if it's going to be a long one. Your log tells you what your thinking was at a particular stage of a project, so if you read your log, it's easy to get back into the flow of a long project like a book, if you've had to abandon it for a while.
Many years ago, I also kept a long for my writing goals. At the time, I was much more goal-oriented, and much more excited about achieving goals. Keeping a log of my goals, and my daily progress towards them, kept me focused.
I've decided to start keeping a writing goals log again.
Try keeping a writing log. Make a commitment to keep it for at least a week, before you give up on it.