If you are in your head a lot like I am, writing down your thoughts is a great way to get rid of them. It also allows you to see everything clearly in front of you rather than just in a big bundle of randomness in your mind.
I am one of those people who know the HUGE benefits of journaling, yet rarely do it myself. I start off well but often get distracted. If there is one thing I would like to get better at this year it is this as it can be great for simple things like a to do list for the next day but also for bigger issues that are on your mind and you would like to either clarify or get rid of.
I might not journal everyday, but one thing I have kept to and found immensely useful is noting my mood changes daily. This can be as simple as a smiley / sad / indifferent face next to a calendar date, or a slightly more in depth descriptions in a diary. One thing that used to worry me was that I didn't know when I would feel down or why, plus you always think you must be the only person in the world feeling this way and then you over analyse and overthink your thoughts.
I have noticed however, that a lot of my emotions are really linked to my hormones and cycle, plus when I drink too much I can feel blue for a few days afterwards. This takes off some of the pressure of thinking it's just me as a person but rather a simple hormone imbalance is to blame at the time. It also lets me acknowledge that the feelings are temporary as I can see the same happened last month/ last time and I survived.
I have provided a few journaling ideas and prompts to get you started here if you think that journaling would benefit you. You might feel a bit silly at first but overtime it will just become a way of life.