What is Self-realization?
Self-realization means self-discovery in the highest sense of the term. One realizes one's oneness with God consciously. Now you have studied books and people have also told you that God is in everybody. But you have not realized God in your conscious life.
In order to realize what realization is, we first have to love our inner Self. The second step is to love realization itself. This is the love that awakens the soul. This is the love that illumines our consciousness. Love and you will be loved. Realize and you will be fulfilled.
/Can we actually feel our realization coming, or does it appear spontaneously and unexpectedly?/
Real realization cannot dawn unexpectedly. Gradually, gradually we come to the point where we realize God. If one is on the verge of realization, he will know that it is a matter of days or months or years. Realization is complete conscious oneness with God. Now, if one does not have a limited conscious oneness with God, how can he attain an unlimited conscious oneness with God all at once?
/What is the difference between a mystical experience and God-realization?/
God-realization is infinitely higher than a mystical experience. In a mystical experience, you feel God's Presence as something very sweet and delicate, but a mystical experience is not a permanent thing. As soon as you achieve a mystical experience, you can lose it. But God-realization you cannot lose; it is permanent. Once you realize God, you never lose what you have