It is very important that your main internal narrative is something wholesome, upbuilding, principled. So often the media or current thought is more dominant than other voices. Learning scripture from memory or other good quality texts means the words become a part of you. You are not dependent on having a book or a being able to go online.
Memorising words is not just a trivial mental exercise. What dominates your mind will be revealed in actions. Peter writes, ‘prepare your mind for action’. This describes succinctly the impact your thoughts can have on your outward actions.