Ultimately, in its highest sense, self-sacrifice means to give our will and our all to God to do with as He pleases. Then He purifies and glorifies our true self until it becomes a shining and wonderful reality.
(Shoghi Effendi, Lights of Guidance, p. 113-114)
What every believer, new or old, should realize is that the Cause has the spiritual power to re-create us if we make the effort to let that power influence us, and the greatest help in this respect is prayer. We must supplicate Bahá’u’lláh to assist us to overcome the failings in our own characters, and also exert our own will power in mastering ourselves. However, unfortunately, not everyone achieves easily and rapidly the victory over self.
(Shoghi Effendi, Lights of Guidance, p. 113)