It’s a way to stay organized, focused, and motivated. if you just sit there thinking random thoughts and then the next day you forget what they were then it’s going to take you a lot longer to get to your destination- it’s like setting out on a trip without a map and you very often end up going in circles. Get yourself a notebook that appeals to you; one you’d like to write in. Get yourself some brightly colored pens to use. Or, if you prefer using your computer, tablet, or phone then do that instead. You know what works for you and what you gravitate towards.
But putting your thoughts down someplace where you can read them and review them will make all the difference.