Dama is self-restraint. It is control of the senses. It is a vedantic sadhana (practice). It comes after the practice of sama (restraint of mind). It is one of the sad-sampat (six-fold wealth). It does not allow the senses to run outwards. It gives strength, peace and concentration. It develops will-power. It helps you to disconnect or shut off the mind from the senses, and the senses from the objects. It corresponds to pratyahara (sense-withdrawal) of raja yoga. An objector says, "Why should there be practice of dama when the mind is controlled by sama?" It is a double attack on the mind. The mind operates in conjunction with the senses; the mind will be subdued easily and effectively if you practise dama also. It weakens or thins out the mind.
There is also a deliberate order here. Without viveka (wisdom), vairagya (dispassion) is not powerful. It is viveka that weans the mind from sensual objects and directs it towards the Absolute. So viveka comes first. If there is dawn of viveka, vairagya, serenity (sama) will come by itself. It is easy to control the mind if the senses are also controlled. So dama comes after sama. If you practise dama, uparati (satiety) follows - you are disgusted with sensual objects. Serenity and restraint of the indriyas are increased if you have titiksha or power of endurance. When you possess the above qualifications naturally you will have faith (shraddha) and a balanced inner life (samadana). If you are endowed with viveka, vairagya and six wealths, a burning yearning for liberation (mumukshutva) will automatically follow.
Sensual pleasure is the womb of pain. The cause for pain is the pursuit of pleasure. Sensual pleasure is imaginary, illusory, fleeting and tantalising. Abandon pleasure and rejoice in the eternal bliss of the Atman. He who has destroyed desire is really a harmonised, peaceful and happy man.