This is not only good writing but also good therepy. You never know how things change when you look at them from another perspective. There are no hard and fast rules to keeping a journal. Some people like to type on thier computer while others prefer to use a pen. Some people use a sketch book so that lines do not limit them while others prefer lined paper.
Some people like to use the same type of book for every journal in thier library.
I use all kinds of notebooks. My only requirement it that they are appealing to the eye. I have some with flowers on them and some with cartoons. You might be amazed at what you find. An itegral part of your education as a writer is keeping a journal.