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 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.