As there can be yin and yang of many things so there can be flows of many things. The flow of chi throughout the body at rest and in energy meditation. If any chakra/lateefa is blocked it will cause the thoughts and the emotions like fear to get trapped in those vortices. There the flow of blood and plasma and lymph fluid. The flow of shariyat and tariqat. The rotational flow of yin and yang. The flow of bowel from the intestines. The flow of knowledges. The flow of heat from area of high heat to the area of low heat. Flow of colors. The flow of nerve impulses. The flow of effortless deep breathing. The flow of Nur from Murshid to mureed during tawaju. Whenever the flow is distorted, you get depression.