Meditation has been shown to decrease symptoms and burden of atrial fibrillation. I practice it daily and also recommend it to my patients.
I started meditation at age 7 and had been practicing intermittently until about 5 years ago when I saw this Jerry Seinfeld video. After this I started practicing daily.
If you are a religious person, your church or temple or mosque probably offers resources for it. Prayer has some of the same characteristics as meditation.
In the event that you are “spiritual” but not religious or an agnostic or atheist, meditation can be similarly effective.
Here are some resources that I have tried personally:
https://www.ymcanoco.org/health-fitness/fitness-classes/spirit-mind-body