Sadhana means to practice something as a discipline, in order to learn from it, and make it a regular life habit.
In Sikhism, the term sadhana is used primarily by Western Sikh converts and refers to a spiritual discipline or practice, usually involving chanting and Kundalini yoga as taught by the late Yogi Bhajan, a system which has its roots in Hinduism, rather than mainstream Sikhism. Students of Kundalini may engage in ashram group living to have sangat for the purpose of practicing yoga and meditation during early morning Sadhana to effect positive changes in life and consciousness.
A typical ashram sadhana might begin with rising about 4 am, bathing, and engaging in 30 - 60 minutes of a specific set of yoga exercises, incorporating postures, breathe techniques and chanting of mantras.
A special sadhana discipline might begin as early as 2 am and could involve 11 minutes, 31 minutes, or even 2 1/2 hours of chanting for a set period time which could last anywhere from 40 days to 1000.
Morning sadhana is often followed by reading of Japji, first of the morning prayers, and the traditional Sikh worship service including, singing devotional hymns of kirtan, and reading hukam, a random verse from the scripture of Guru Granth Sahib.
Fifth Guru Arjun Dev who compiled the scripture of Guru Granth Sahib, wrote of the futility of ritual discipline, stressing that neither mind, nor body, can be cleansed of egoism by methods which bolster pride, except by contemplation of naam.
"Man kaamnaa teerath daeh chhuttai ||
Your mind teeming with desire, you may give up your body at a sacred shrine of pilgrimage;
Garab gumaan na man tae huttai ||
But even so, egotistical pride shall not be removed from your mind.
Soch karai dinas ar raat ||
You may practice purification rites of cleansing day and night,
Man kee mail na tan tae jaat ||
But the filth of your heart shall not leave your body.
Es daehee ko bahu saadhanaa karai ||
You may subject your body to all sorts of disciplines,
Man tae kabhoo na bikhiaa ttarai ||
But your mind will never be rid of its corrupt passions.
Jal dhovai bahu daeh aneet ||
You may wash this transitory body with much water,
Sudh kehaa hoe kaachee bheet ||
But how can a mud wall be washed clean?
Man har kae naam kee mehmaa ooch ||
O my mind, the Glorious Praise of the Lord's Name is the highest;
Naanak naam oudharae patit bahu mooch ||3||
O Nanak, the Name has saved a great many of the worst sinners." ||3|| SGGS||265
The writings of Bhai Gurdas, who lived from 1551 until 1637, are respected as the key to understanding the scriptural texts of Guru Granth Sahib. He stressed that reciting the mantra of truth is the highest discipline and this only is capable of eradicating ego:
"Gursikh sabho saadhanaa saadh sadhaae saadh sadhavaaiaa||
The Sikhs of the Enlightener Guru can be called disciplined only with disciplined achievement after accomplishing many disciplines." Var 7
"Sachu ourai sabh kihu sach naao gurmant dhirraaiaa||
Truth is highest above all, and the true name is the only effective gurmantar (enlightening mantra) to be recited with utmost integrity." Var 7
"Saadhsangat kar saadhanaa ek man ek dhiaaee||
In the company in the Holy ones he disciplines himself and is rid of his ego, only then he remembers the Lord with single-minded devotion." Var 9