One of the most important of these ceremonial functions is called Ūrja-vrata. Ūrja-vrata is observed in the month of Kārttika (October-November); especially in Vṛndāvana, there is a specific program for temple worship of the Lord in His Dāmodara form. "Dāmodara" refers to Kṛṣṇa's being bound with rope by His mother, Yaśodā. It is said that just as Lord Dāmodara is very dear to His devotees, so the month known as Dāmodara or Kārttika is also very dear to them.
The execution of devotional service during Ūrja-vrata in the month of Kārttika is especially recommended to be performed at Mathurā. This system is still followed by many devotees. They go to Mathurā or Vṛndāvana and stay there during the month of Kārttika specifically to perform devotional services during this period.
In the Padma Purāṇa it is said, "The Lord may offer liberation or material happiness to a devotee, but after some devotional service has been executed, particularly in Mathurā during the month of Kārttika, the devotees want only to attain pure devotional service unto the Lord." The purport is that the Lord does not award devotional service to ordinary persons who are not serious about it. But even such unserious persons who execute devotional service according to the regulative principles during the month of Kārttika, and within the jurisdiction of Mathurā in India, are very easily awarded the Lord's personal service.