The mind is constantly occupied with thoughts. There is no gap or vacuum in this process. These thoughts are either of worldly matters or useless issues or sinful activities. It is essential to intervene and develop a spiritually healthy though pattern. We have to actively think about hereafter, heavens, thankfulness of Allah for the innumerable bounties and blessings bestowed upon us, asking refuge for anticipated calamities, repenting from sinful activities, etc.