When the Jews recieved the Torah, even though they had the right idea by saying we will do whatever it states, nonetheless the reason they said this was a reaction to the incredible love G-d had shown them (but when that love was witheld they said "lets go back to Egypt") When the Jews in the times of Mordechai and Esther said "we will do the Torah," that was because the sword of haman hung over their head – but when a Jew today says "I will do the Torah!" He does so out of pure love/convicton – a choice which is eternal