Journaling my thoughts and experiences has been my most impactful and healthy habit I started doing in life.
I started with journaling by writing Day Evaluations, evaluating my day and noting interesting and memorable things that have happened to me during the day.
Journaling helps me be mindful of what I am doing and keeps me in check for what my thoughts on life are at any given time. I can be brutally honest with myself when writing there and for me its part of a cleansing process of bad and negative thoughts I feel.
If I ever feel down, I can just start writing and just release all these negative thoughts onto paper. Many times, the simple act of writing makes you realize that these things I worry about are silly and are either not in my control or simply not worth even being sad over.