Sri Aurobindo
Letters of Sri Aurobindo
03. Basic Requisites of the Path
Yes, of course you are right. The process of surrender is itself a Tapasya. Not only so, but in fact a double process of Tapasya and increasing surrender persists for a long time even when the 
surrender has fairly well begun. But a time comes when one feels the Presence and the force constantly and more and more feels that that is doing everything – so that the worst difficulties cannot disturb this sense and personal effort is no longer necessary, hardly even possible. That is the sign of the full surrender of the nature into the hands of the Divine. There are some who take this position in faith even before there is this experience and if the Bhakti and the faith are strong it carries them through till the experience is there. But all cannot take this position from the beginning – and for some it would be dangerous since they might put themselves into the hand of a wrong Force thinking it to be the Divine. For most it is necessary to grow through Tapasya into surrender.