A true Yogi(practitioner) is one who has acquired self-knowledge and through continuous practice and detachment has been able to rest in true self, so firmly that he seldom slips down from it. Samadhi is the state where one realises the true self or soul. When true self is realised everything is realised.
There are three kinds of Samadhi - Samprajnata(conscious), Asamprajnata(supraconscious) and Jada(inert). Let us first see what Samprajnata Samadhi is. Patanjali describes - Samprajnata is achieved by following argument(vitarka), analysis(vichara), bliss(ananda) and egoism(asmita)(I.17).
When a Yogi turns away from all those things that are either seen or heard of, he begins to think about himself, like - who am I; why I am here; what to do here; what this world(samsara) is; who is God and where does He lives. In this way many arguments(vitarka) appear in his mind. In order to know the truth he reads scriptures, listens to wise people and starts analyzing(vichara) what he learnt. A true analyst always ends up with the truth. Upanishads have glorified human beings and soul(atman). atman has been described as Brahman, the ultimate reality. So after right analysis when a Yogi finds out that he himself is that glorified super being, he feels the bliss(ananda). This develops egoism(asmita) in him, as there is none greater than him. In this way and with these thoughts a Yogi enters into Samadhi and realises himself. This is the Samprajnata(conscious) Samadhi.
Then comes the Asamprajnata(supracoscious) Samadhi. When a Yogi enters into Samadhi regularly he becomes so much adept in this practice that he no longer thinks about practice, detachment or true self. All of these become part and parcel of his body and mind. Whenever he wishes he enters into Samadhi. Patanjali describes Asamprajnata Samadhi as - the state where practice for controlling of thoughts remains merely as memory(samskara), becomes Asamprajnata Samadhi which is other than the Samprajnata Samadhi(I.18). In this state, thoughts, controlling of thoughts, practice and detachment; all these things remain as memory or impression. One only feels the bliss of true self. This state cannot be described adequately.
Then let us see what Jada(inert) Samadhi is. In both the Samprajnata and Asamprajnata Samadhi consciousness is never lost. These are such sleeping states where one is waking and fully conscious. A conscious being should not try to become unconscious at any state. However many people try to enter into Samadhi unconsciously. They remain unconscious for several hours/days. This is Jada(inert) Samadhi. Patanjali describes - the state of unconsciousness(videha) and disappearing into the material world(prakritilaya) is due to the act of inertness(bhava)(I.19).
Unconsciousness is the state where one is not aware of one's own body, mind or self. It is like entering into a comatic state. One disappears into material world and becomes as good as or as bad as matter. So instead of trying to become a material thing one should try to become more conscious, gracious, blissful and intelligent. Unconsciousness is a disease in Samadhi.
One who thinks that soul is separate from and inferior to God, one cannot realise one's true self and enter into Samadhi. Only a Yogi who knows that soul is not different from God, may enter into Samadhi. for this Patanjali instructs - by bearing(pranidhan) God(Ishvara) in oneself(I.23). One should bear God in one's heart of deeper mind. For most people it may seem highly improbable, because how God may be carried in one's heart. For this Patanjali dscribes who God Is. Any human being(purushavishesh) who has separated himself from those evil thoughts which generate such fruits of action that give pain is God(Ishvara)(I.24). So one is God who has dispelled all evil thoughts from the mind. Evil thoughts may be controlled when one realises that soul is God and when one bears Godliness qualities in himself. By this he transforms himself from a mere mortal being to God. Krishna, Buddha, Jesus and Mohammad were all God. They had imbibed all those divine attributes which people believe to exist in God. All these divine attributes emanates from soul(atman) for this the aim of Yoga is to realise true self
