In Guru Vachaka Kovai, Bhagavan Sri Ramana Maharshi tells us:

734. Those who have one-pointed devotion towards God, like the magnetic needle [of a ship’s compass] which always stands facing towards the north, will never be perplexed and go astray in the ocean of attachment of this world.

735. Those who live in the world, clinging whole-heartedly to God, are like children who whirl round and round a pillar holding it firmly. Since they have a strong and unshakeable hold on God, they are devoid of ego [anava] and therefore will never fall a prey to the delusion of the world.

736. If one fixes one’s mind firmly on that pure Supreme Reality which pervades all activities, one will not be affected by any number of activities that are done.