Writing down your thoughts and emotions on a daily basis can help you have a clearer understanding of what's going on in your mind. It provides you with the opportunity to look at your problems and challenges from a different perspective and to come up with solutions more quickly. Writing also allows you to self-reflect without judgment and view things subjectively. Moreover, as you begin writing, your awareness starts to shift and expand, which can help you become more imaginative and creative and explore new possibilities.
You can always come back to your notes later with a fresh mind and see how different your emotions and thoughts may have become. This helps you realise that your thoughts and emotions can change quickly and therefor can not always be relied upon when it comes to making important decisions or taking necessary actions. And finally, journaling can improve your writing skills, which is helpful in all aspects of life.