The Shulchan Aruch states that when a person is davening Shemone Esray (Amidah), it is forbidden to walk within 4 amos (which is 6-8 feet) in front of him. The Chayei Odom points out that the reason is because then you come between the person davening and the Shechina (Hashem’s presense).
4. Be kind to yourself. Speaking badly even about yourself is unethical.
הלכות שמירת הלשון 