Question : Having heard this truth, why does not one remain content?
Ramana Maharshi : Because samskaras [innate mental tendencies] have not been destroyed. Unless the samskaras cease to exist, there will always be doubt and confusion. All efforts are directed to destroying doubt and confusion. To do so their roots must be cut. Their roots are the samskaras. These are rendered ineffective by practice as prescribed by the Guru.
The Guru leaves it to the seeker to do this much so that he might himself find out that there is no ignorance. Hearing the truth [sravana] is the first stage. If the understanding is not firm one has to practise reflection [manana] and uninterrupted contemplation [nididhyasana] on it. These two processes scorch the seeds of samskaras so that they are rendered ineffective.
Some extraordinary people get unshakable jnana after hearing the truth only once. These are the advanced seekers. Beginners take longer to gain it.