There are few words in the English language to adequately the various states of ecstasy and self realization which one can experience. The all-encompassing term commonly used to describe the advanced states of consciousness exhibited by such great sages as the Buddha, Paramahansa Yogananda, and others, is Samadhi. But there are thousands of Yogis (those who seek union with God) in the world who experience this great state of peace and enlightenment. Anyone who is sincere in their practice and desire to see God has the hidden potential to dip into this remarkable state of consciousness.
In the Kriya Yoga tradition, Samadhi is a physical state of suspended animation, where breathing and heartbeat are stilled, accompanied by a focused mental state that facilitates profound insights into the true nature of reality. Samadhi can be triggered by prayer, meditation, kriya/chakra/tantric yoga, self-sacrifice, good works, near-death experiences, and more. Few Western religions prepare one for such an experience, and those who are blessed with it are often described as having undergone tremendous agony and sacrifice. But this is not necessary. One can turn to Eastern religions which have studied the subject in a more scientific manner, documenting which practices help the experience, and which ones to avoid.
Most people see Samadhi as unobtainable - they feel they are not "religious" enough, physically fit enough, or have too many worldly habits. The Kriya Yoga practices help us to deal with and overcome these human frailties. Many people begin to experience periods of breathlessness after about 2-3 years of intense practice of Kriya Kundalini Pranayama. Know that Samadhi is attainable!
Popular Kriya Yoga lessons and literature seem to get people thinking of Samadhi and self-realization as one and the same thing. True self-realization might take 30 years of intense practice, but Samadhi does not. Samadhi is the medium for attaining self-realization. The great Master Yogananda says to enjoy the periods of breathlessness that follow Kriya Kundalini Pranayama. And that is exactly what should happen.
It usually takes some personal instruction to get beyond the initial stages of Samadhi. Yogananda talked about his techniques as a method for building and tuning a sensitive radio for communicating with God. The point missed by many is that, once you build and tune the radio, you should listen to what God is personally telling you. Often, when the time is right, a teacher will appear nearby. Yogananda stressed that one must not be timid in one's approach if one wishes to attain self-realization. Yet many students are so timid that they refuse to consider anything that is not in the printed lessons, and they are blind to their final instructions. It's kind of like learning how to read, and then, instead of using that skill to read great texts on religion and philosophy, just reading the same ABC learn to read books over and over again, because those are the only ones your teacher used in school.
One must not be timid in one's approach if one wishes to obtain self-realization. One must thirst for knowledge. One must seek it unceasingly. One must develop and trust a deep intuition for what is right. One must expect results. One must overcome any fear that one is not deserving of the sweet nectar and the great prize.