Raja yoga is an exact science. It aims at controlling all thought-waves or mental modifications. It is concerned with the mind, its purification and control. Hence it is called raja yoga, i.e. king of all yogas. It is otherwise known as ashtanga yoga, i.e. yoga with eight limbs.
The eight limbs of ashtanga yoga are: yama, self-restraint, niyama, religious observances, asana, posture, pranayama, restraint of breath, pratyahara, abstraction of senses, dharana, concentration, dhyana, meditation, and samadhi, super-conscious state.
Yama is the practice of ahimsa, non-injury, satya, truthfulness, asteya, non-stealing, brahmacharya, celibacy, and aparigraha, non-covetousness in thought, word and deed. This is the foundation of the niyamas: shaucha, internal and external purity, santosha, contentment, tapas, austerity, swadhyaya, study of religious books and repetition of mantras, and Ishwara pranidhana, worship of God and self-surrender.
Cultivate maitri, friendship with equals, karuna, mercy towards inferiors, mudita, complacency towards superiors, and upeksha, indifference towards wicked people. You can eradicate jealousy and hatred and attain peace of mind. Ascend the ladder of yoga patiently through its different rungs and attain the highest summit of the ladder, i.e. asamprajnata samadhi, wherein all samskaras, impressions, which bring about successive births are absolutely fried up.
If you really aspire to unfold the lurking divinity within, if you really want to get rid of the meshes of this samsara, you must know the technique of thought-control which is embodied in the system of raja yoga. You must know the ways of right living, right thinking, right speaking and right acting. You must practise the five rules of yama or right conduct or sadachara. You must know how to withdraw the mind from external objects and fix it on one point. You must know the right method of concentration and meditation. Then alone you can be really happy.
Then and then alone, you will have power, independence and suzerainty. Then and then alone, you will attain immortality, freedom and perfection. Knowledge of the ways and habits of the mind, its operations, the laws of the mind and the methods of mind-control and mental discipline is very necessary if you want to enjoy real happiness and peace of an unruffled and abiding nature.
Practise raja yoga, control the thoughts, discipline the mind, meditate regularly and attain independence, immortality, freedom and perfection.