Call it a diary, if you wish, but it is so much more than just writing about the cute guy in your history class. A journal should be kept for many reasons and I guarantee it will help you in some way. I have kept a journal for about a year now and it is interesting to look back (or never look back) on the pages that describe a certain period of your life, whether they were challenging or joyous times.
I keep a journal to remember important things or plan out future events. It is helpful to have a place for important dates and things I need to remember by just jotting a note down in my journal. I also use it to make lists of things I need to do or things I need to buy. I also use my journal to set goals and lists of things I strive to accomplish over time. Although, just because I have written them down does not make them permanent. The lists are subject to change over time and things may be added or dropped from the lists, as life is always changing. Yet writing things down is the easiest way to make them real; they go from just an idea floating around your head to a solid form on paper.
I use my journal to document things that have happened to me that day whether it is just what a great day I had or if I feel the need to rant about the drama in my life. This helps me organize my thoughts and how I should respond to a certain situation happening in my life. Most of the time when I write about something that is just so terribly awful I realize that things are not as bad as they seem. Most of the time writing helps me clear this up so much that I am able to compose a way of dealing with said situation.
A journal can also double as a prayer journal. It is convenient to use my journal for religious reasons as well instead of having a separate prayer journal. I use it to take note of important verses that I have found and wish to remember, and I love coming across these verses later. I can write out prayers or even recap things that I learned in church and wish to look on back down the line. My journal is a personal and private place to write about virtually anything.
A journal can serve as so much more than just a diary and there is no shame in keeping one. I enjoy having a personal place to write down everything that seems to be swirling around in my head throughout a hectic day. You will thank yourself later when you thumb across a note that you have a math test on Friday that you may have let slip your mind due to the three trillion other things you have had going on this week. Keeping a journal has helped me organize my thoughts, keep notes, set goals and ultimately keep my life (somewhat) in check, and I highly recommend it.