Energy at different levels is known by different names. At the highest level it is called spiritual experience. On the emotional level it is known as love. On the physical level it is known as sex, and at the lowest level it is known as avidya or ignorance. So therefore, when you talk about sex, you must understand that it is only a particular formation of energy. Just as curd, butter and cheese are different formations of the one thing – milk, energy has different manifestations. Matter is the grossest manifestation of energy; in the ultimate state, matter is energy. Therefore, energy and matter are intra convertible. The same energy which flows through passion, the same energy when channelized, manifests as devotion. Channelize this same energy again and it manifests as spiritual experience. That is why spiritual aspirants love God in various manifestations. Some picture him as a father, a mother, a child, a friend, husband or lover. In this way, they can sublimate the form of their emotional energy and even transform the primal energy into a divine experience.. When kundalini is ascending from mooladhara to swadhisthana, the sadhaka experiences a crucial period in which all his repressed emotions, especially those of a more primal nature, express themselves. Passions mount during this period and all kinds of infatuations ensue, making the sadhaka extremely irritable and unstable at times. It must be remembered that up to swadhisthana chakra , the consciousness is not yet purified.
Due to ignorance and confusion, the psychic powers awakened at this level are often accompanied by maleficent mental attributes.( Note that psychic abilities are associated with kundalini ascension not partial prana ascension, partial prana ascension creates only disturbing mental/physical attributes as a part of partial purification process). What happens here when the aspirant tries to manifest or express himself through the psychic medium is that more often than not it becomes a vehicle for personal and lower tendencies rather than for the divine.The sum and substance is this – awakening of kundalini is not a difficult task, but to get beyond swadhisthana is. For that you must improve the general background of your psycho-emotional life. Once you pass swadhisthana you will not have to face any explosive traumas again, but there will be other difficulties further on. Kundalini is unlikely to descend again as it is destined to move on, but the problems you will confront will be concerned with siddhis (psychic powers), and they are more difficult to subdue..When no sexual desires of any kind manifest in an aspirant any more, and when there is no more personal attraction, that means kundalini has passed beyond swadhisthana chakra. However, when dealing with the subject of sex, your understanding must be very thorough. Although you may not be having any sexual awareness at the moment, that doesn’t mean your desires have been exterminated. They might be in a suppressed state. There is an automatic process of suppression in the human constitution, and that is inherent in our own mental being. Yogis have stated that sexual awareness and desires can manifest at any stage of evolution. They are very acute and clearly expressed when one is in swadhisthana and having continual fantasies, but sexual awareness never really dies because it is fueled by the primal energy which is present all throughout. Sex is only an expression of that, and therefore it can manifest at any stage, and one should never think that he has transcended it. It is even present when one is in the highest state of consciousness. The only difference is that in swadhisthana it is in a very disturbed state, whereas in the higher centers of evolution it is in a seed form. After all, what is bhakti or devotion; what is union? They are the sublimated pure form of sexual energy. When kundalini is residing in swadhisthana chakra, the last vestige of karma is being thrown out and all the negative samskaras express themselves and are expelled. At this time you may be angry, afraid or full of sexual fantasies and passion.
A yogi who had difficulties getting through swadhisthana chakra wrote: “I was sitting all night and nothing but sex and sensual thoughts came to my mind. And I dreamed of many women presenting themselves in their naked form, and my whole body was becoming hot and cold, hot and cold. Ultimately I got a headache, and at one point, I thought my heart would collapse. “Throughout the crisis, my guru’s face used to come like a glimpse. His face was stern and expressionless, and that used to bring my temperature back to normal. However, this confrontation I was having with a powerful side of my mind continued until morning. At last, when morning came I breathed a sigh of relief. But then, when I sat for meditation in the evening, I had mixed feelings. I had fear in my mind and confidence as well. “Day in and day out the mind played its tricks on me. Then one night Parvati came to me. Parvati is the shakti of Lord Shiva, and she is the divine mother. I knew she was Parvati, but because she looked so beautiful and she was wearing almost transparent clothing, I began to desire her. Rather than remembering that she was the divine mother, my mind was more aware of the form behind the transparent apparel, “Like a flash of lightning my guru showed his face and I regained my senses and prayed, ‘Mother, withdraw your maya. I can’t face these experiences. You are the giver of liberation and you are the creator of illusion. You have the power to cast me back into the cycle of birth and rebirth and you have the power to lift me from this quagmire of ignorance.’
“As I prayed, tears rolled down my face and I felt a cool breeze passing through the interior of my body. The whole panorama vanished and I understood that kundalini had passed through swadhisthana and was now heading towards manipura.”
Ref – Kundalini Tantra