One way to improve your mental health and well-being is to start journaling. Writing down your thoughts and feelings allows you to process them in a healthy way and to slow down your mind. Think of it like making a grocery list - instead of going to the store and repeating to yourself milk, butter, eggs - you write it down, and move on.
Scientific studies have shown that journaling can be beneficial. Journaling has been found to boost mindfulness, memory, communication skills, improve sleep, self-esteem. It has even been shown to improve immune system functioning and reduce blood pressure. And you don't have to write much. Research has shown that even 15 minutes of writing can have beneficial effects. Journaling about what you are grateful for every day has been shown to increase happiness (as a side note - I know everyone says this one and it can be annoying to hear it over and over again, but I highly encourage you to just try it for a few days and see how it goes, as many have found it life changing).
Why is this the case? Journaling can help you label your emotions and thoughts and make sense of difficult things in your life. Journaling can help you process something - to get unstuck. It is hard to write about something and over again without doing something about it.
Reading old journals can be helpful too. You can look back at your life and see how you made it through hard times, and have confidence that you can do hard things in the future.
So how do you get started? Dr. Pennebaker, one of the first and most-renowned researcher on journaling and expressive writing, recommends setting aside 15-30 minutes on four consecutive days and writing about one issue that is causing significant anxiety or pain. I also recommend Let it Out as a book to help people get started.