Self-realization happens all at once, as a big bang - it cannot happen otherwise. Meditation practice can lead you to it, but it does not, strictly speaking, causes it. It has been said that self-realization is an accident, and meditation makes you accident-prone. If you meditate for very, very long, you will become extremely accident-prone and it may happen anywhere, anytime. Effort is required, but a relaxation is also required.

Enlightenment happens gradually after self-realization, but not through practice. Practice becomes impossible afterwards, every effort becomes counter-productive. If one feels any need to practice, self-realization hasn’t happened, leave alone enlightenment. But meditation does speed up the progress from self-realization to enlightenment, and one often feels a natural urge to meditate or becomes sleepy.