must be chanted with complete dedication for 108 times and to get blessings and protection from the deity.
you can chant it 108 times daily, especially on Tuesdays.
ॐ केतुं कृण्वन्नकेतवे कष्टो मर्या अपेषसे। समुषद्भिर्जयथा:।।
"Om Ketun Krivannketave Pesho Marya Apeshse. Samushadbhirjayatha:"