In Prashanthi Vahini Swami explains:

Even for being blessed by the Lord’s Grace, One must have Santhi and await patiently. Serenity alone succeeds in bringing about the result of Sadhana. Add this lesson to the practices you are engaged in, night and day, and to the Santhi Manthra.

Asatho Maa Sadgamaya
Thamaso Maa Jyothirgamaya
Mrityor Maa, Amritham Gamaya

This is the Santhimanthra. The meaning of this mantra is given variously by various people, some elaborately, some succulently.

• “O, Lord, when I am deriving happiness through the objects of this world, make me forget the unreal objects and show me the way to permanent happiness,” This is the first prayer.

• “O Lord, when the objects of the world attract me, remove the darkness which hides the all – pervading Atma, which every such object really is.” This is the Second prayer

• “O Lord, bless me through your Grace with Immortality or paramananda, resulting from the awareness of the Effulgence of the Atma, immanent in every object.” This is the third prayer. This is the real meaning of the Mantra.

The true Bhaktha will always be dwelling in God. He has no time to know or feel his welfare or worries. Attaining the Lord, is the one and only idea in his mind. It is hard to understand this nature, except by examples. A small child runs about in fear shouting, “Amma, Amma”, searching for its missing mother. The mother takes it up in her arms and places it on her lap. The child stops crying and is free from all fear. But, can the child calculate and find out the difference between its previous state and its present relief? No. Nor is it necessary to do so.

So too, he who seeks ever to serve the lord will immerse himself in it when the glorious chance comes; in that presence, no anxiety or trouble can disturb him. Anxiety and trouble pester only until the moment of attainment; then, all attention is diverted to the Experience. The past struggle and travail are forgotten.

[Ref: http://saibaba.was/vahini/prashanthivahini.html]