Writing has been known to contribute a great deal to healing, relaxing, and overall relieving of any stress. When you free write it's almost as if you're seeing a therapist minus the cost. You can vent, let out all of your feelings, including the not so nice ones, and the only person who gets to see it is you.
One of the many things Gabby Bernstein has taught me, is that if you feel hostility or resentment toward an individual, the best way to rid yourself of those negative feelings is through writing to them. Yes, writing to them. Just because you write to them does not mean you have to give it to them. You can write a letter to them letting go of whatever it is that needs to be, and then sign it "With love".
I've done this several times. After making a compassion list of all the people who I felt any sort of discomfort with, I have written them letters expressing my anger, frustration, and resentment. On the last line of the letter I would say "I forgive you and I release you. With love, Brittany". It sounds silly, but it works. If you continue to have the "forgive and release" mentality, you will live with zen. Start by writing letters to those you can't seem to let go of something you feel they've done to you.
In a way writing these letters is an agreement to yourself, because after all you are the only person who feels this way, the odds of the other person feeling upset about what he/she did are slim. Since you wrote out all of your feelings toward a particular person/people, you agree to never go back to those old ways and from now on see them with only love. You wrote the letter of how that person "wronged" you, you forgave him/her, and you released him/her. Simple, easy, and affective.