Yoga and Spirituality means PURITY. I practice Yoga or Spirituality means I practice Purity in feelings, thoughts, words and deeds.
An impure body/individual can’t practice Yoga or Spirituality.
One, whose body doesn’t have pure blood and mind doesn’t have Purity or Vairagya can’t sit for a long for the meditation. And if there is no meditation, there is no Samadhi. Meditation only leads more deeper into Samadhi (Full absorption into Transcendental State).
Through the practices of Yama and Niyama one purifies the mind and through the practices of Asanas, Pranayama, Bandhas and other Hatha Yogic Kriyas one purifies the blood of the body. These are the preliminary but essential practices of Yoga and Spirituality, through which mind and body get purified, then one becomes eligible to sit for Concentration Developing Practices like Nasikagra Mudra, Shambhavi Mudra and Trataka (Gazing) on any object, be that wall, the flame of a candle or lamp, or the moon or the sun or any other specified object.
And when Concentration is developed up to the optimum point, then one qualifies for the Meditation, and when one enters deep into meditation, only in that condition one can practice the Samadhi (Absorption).
Samadhi is the Meaning and pointing of Yoga and Spirituality. Samadhi is of two kinds Sawikalpa/Sarupa/Sabeeja/Bhawapoorna Samadhi and Nirwikalpa/Arupa/Nirbeeja/Bhawaateeta/Transcendental Samadhi.
A rebellious one only can enter into second/highest kind of Samadhi i.e., Transcendental Samadhi.