When one hears about the Lord and glorifies Him, it is natural to think of Him. This is called smartavyah. All this must be carried out if one actually wants to be immune from fear
"'O descendant of Bharata! O Mahārāja Parīkṣit! The Supreme Personality of Godhead, who is situated in everyone"s heart as Paramātmā, who is the supreme controller, and who always removes the miseries of the living entities, must always be heard about from reliable sources, and He must be glorified and remembered by one who wishes to become fearless.'"
This is a quotation from Śrīmad-Bhāgavatam (2.1.5). It is one's duty to understand the Supreme Personality of Godhead through the hearing process. This is called śrotavyaḥ. If one has heard properly about the Supreme Personality of Godhead, his duty is to glorify the Lord and preach His glories. This is called kīrtitavyaḥ. When one hears about the Lord and glorifies Him, it is natural to think of Him. This is called smartavyaḥ. All this must be carried out if one actually wants to be immune from fear.