If you simply say without real inner feeling “I am Thine, O Lord”, this will not constitute real integral self-surrender. It should come from the core of your heart. You must be prepared for a radical change. You should not stick to your old habits, ways and motives. You should not expect that everything should happen in the way you want. You should live to carry out the divine purpose. You should not think of those ambitions which the mind likes to gratify. You should not think of using even the divine grace or the divine force for your own purpose. The irrepressible ego will assert in various ways and refuse to give up its old habits and ways. It will try to get everything from the Divine. It will totally decline to give itself to the Divine. That is the reason why aspirants do not make any substantial progress in the spiritual path even after doing Sadhana for several years.
There is no loss in self-surrender. You get from the Lord everything. You enjoy all divine Aisvarya of the Lord. The whole wealth of the Lord belongs to you. Siddhis and Riddhis will roll under your feet. You become one with the Lord. You are freed from all wants and desires and cravings. The spiritually hungry and real thirsty aspirant who yearns for the vision of the Lord turns towards the Divine and is quite willing, eager and happy to consecrate his body, life, mind and soul at the feet of the Lord.
(pgs. 352-353, Sadhana by Swami Sivananda)