They want to know what austerities were performed by the gopis to attain darsana of that form, but only by aspiring to serve Krsna in the mood of the gopis can this be attained. Without an intense hankering for that, it is very, very difficult. No performance of ordinary austerities can bestow the darsana of that form of Krsna which was seen by the gopis. There are so many of us who chant one lakha of harinama daily, and we haven’t received that darsana yet, so what to speak of others? There are many well known austerities, but none of them can bestow this fruit. Some persons sit in the middle of fires in the hot season, and others bathe at four in the morning in the Yamuna in the cold season and then return home in wet cloth regardless of whether it is windy, raining, snowing, whatever. But are there any austerities which, by practicing, we can attain Bhagavan?
aradhito yadi haristapasa tatah kim
naradhito yadi haristapasa tatah kim
antarbahiryadi haristapasa tatah kim
nantarbahiryadi haristapasa tatah kim
Narada-pancaratra
What is the value of austerities performed by sages like Durvasa if they haven’t worshipped Bhagavan, and if they don’t see Bhagavan everywhere? And if one does see Bhagavan within every living entity and everywhere outside as well, then what is the use of any other austerities besides that form of worship? For them there is no necessity of performing any austerities other than observing devotional vows like those for Ekadasi, Janmastami, etc.
Besides taking harinama and hearing and meditating on harikatha, there is no method to attain Krsna’s darsana. The objective of tapasya is to concentrate one’s mind, but catching hold of the wind is easy in comparison to subjugating the wicked mind, so how will it be accomplished? It can only be achieved by serving Vaisnavas, hearing harikatha, loudly chanting harinama, and meditating on Bhagavan.
Bhakti Rasayana page 96 - 97 [CC-by-ND GVP]