Sadhana means Spiritual practice, discipline. Abhyasa and Sadhana are synonymous terms. The object of Sadhana is to release life from the limitations with which it is bound. 

Sadhana is a lifelong process. Every day, every hour, every minute, is an onward march. Obstacles are innumerable in this great voyage. But, so long as you hold God as thy guide, there is nothing to worry about. You are sure to reach the other shore. Mere curiosity will not help you to attain any spiritual progress. Curiosity-mongering is more abominable than mischief-mongering. Introspect. Analyze your thoughts and find out whether you have real spiritual hunger or mere curiosity-mongering. Transmute curiosity-mongering into real thirsting for salvation by constant Satsang (association with the wise), study of good religious books, prayer, Japa, and meditation. 

One should practice one's sadhana according to the guru's instructions.The practice of yoga; the practice by which perfection (siddhi) is attained; spiritual self-training and exercise. Sadhana is spiritual movement consciously systematized. Sadhana is the purpose for which we have come to this place. 

Guru - The Parambrahman

Gurubrahma Guruvishnu Gururdevo Maheshwaraha |
Guruhu sakshaat Parambrahman tasmai Shrigurave namaha ||
The guru is Brahma, Vishnu and Mahesh (Shiva), veneration to the Guru who is Parabrahman manifest.

Who is a Guru? The Sanskrit root "Gu" means darkness or ignorance. "Ru" denotes the remover of that darkness. Therefore one who removes darkness of our ignorance is a Guru. Only he who removes our ultimate darkness, known as Maya, and who inspires and guides us on to the path of God-realization is the true Guru. A spiritual aspirant, no matter how brilliant, can never attain such knowledge by his own endeavor. This is stipulated in the Shrimad Bhagwatam in which Jadbharat reveals to king Rahugan:
"O Rahugan! One cannot attain knowledge of Atma and Paramatma by performing penance, sacrifices, renunciation, Vedic study or worshipping deities of water, fire or the sun. But when the dust from the feet of a satpurush (God-realized Guru) sprinkles on our heads, then we can surely attain this knowledge."
 

Guru Purnima

Guru Govind donu khade, kisko laagu paay,
Balihari Gurudevaki jinhe Govind diyo bataay.
The Guru and Govind -God, are present before me, to whom shall I bow down first? Glory to the Guru since he showed me Govind.

Purnima means full moon day. Guru Purnima is a day for celebration and worship - a day on which the disciples remember and express their gratitude to the lineage of Gurus. A Guru is necessary to make you understand the formless and attributeless Divinity. God, who is attributeless and formless, is the true Guru. In the word 'Bhagavan', the letter 'Bha' stands for effulgence. God who is all pervasive illuminates the entire creation.  Read More