Breathing in a steady calm rate can help our brain waves and mood also become more steady and calm. Health benefits may help the cardiovascular system and reduce oxidative stress. (forbes.com/breathing)
Hypnosis, some types of meditation and yoga, and certain very low frequencies played in rhythm similar to the heart beat also may help calm the brain waves and possibly help us reach a different type of consciousness. (FOIA/CIA-Analysis and Assessment of Gateway Process, cia.gov/pdf) Somewhat similar rhythmic sounds are available on music and/or guided meditation CDs by the BrainSync company or others, an example can be heard online: Remove Mental Blockages & Subconscious Negativity ☯ Dissolve Negative Patterns - Binaural Beats (youtu.be).
Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.