It is said that Krishna reveals Himself at the very end of the devotee’s desperate attempts. King Purushottam Deva, the father of Maharaja Pratap Rudra, once lost a battle. That was the only battle he lost in his entire life. While going back, he met a brahmana who questioned him, “Had you taken the Lord’s blessings?” King Purushottama Deva, in his fury of another king named Salva Narsimha who had promised to give his queen to him but later denied when the king’s ministers saw Purushottam Deva sweeping in front of Lord Jagannatha’s cart, had instantly proceeded to fight without taking the blessings of the Lord. He badly lost. When he realized his mistake after being reminded by the brahmana, he went before the Lords Jagannatha, Baladeva and Subhadra. Whole night he prayed in desperation, and early morning Jagannatha and Baladeva appeared to him and told him that he should go again for the conquest. And this time, We both will be there with you. And sure enough, the next time, he very easily defeated the king.

One time, my spiritual master was chanting sixty four rounds on the Gaura Purnima. He was thinking and pleading to the Lord what he should offer to Him. And the reply came as he was on his sixty forth round, “Your hairs!” That meant total surrender for him. Shrila Prabhupada, in his extending voyage on the Jaladuta, had revelation of Lord Krishna coming in dashavatara form after his two heart attacks.

For Brahmaji, it is mentioned in SB 7.9.35 kālena tīvra-tapasā, Brahma got purified after intense austerities for a long period of time. HH Sacinandan Swami Maharaja also explains this in his book ‘The Living Name’ by stating a story of an elderly Vrajbasi who is serving Lord Krishna in Nandgaon for his whole life, and finally when he is about to go to Barsana in desperation of not getting darshan of Krishna and Balarama, They both reveal Themselves to him. He entitles this story “When Love reaches Boiling Point”.

For elevated souls, when their love reaches boiling point, they get direct darshana of the Lord. As regards to the gopis also, it is mentioned in SB 10.32.1-2,
śrī-śuka uvāca
iti gopyaḥ pragāyantyaḥ
pralapantyaś ca citradhā
ruruduḥ su-svaraṁ rājan
kṛṣṇa-darśana-lālasāḥ
Śukadeva Gosvāmī said: O King, having thus sung and spoken their hearts out in various charming ways, the gopīs began to weep loudly. They were very eager to see Lord Kṛṣṇa.

tāsām āvirabhūc chauriḥ
smayamāna-mukhāmbujaḥ
pītāmbara-dharaḥ sragvī
sākṣān manmatha-manmathaḥ
Then Lord Kṛṣṇa, a smile on His lotus face, appeared before the gopīs. Wearing a garland and a yellow garment, He directly appeared as one who can bewilder the mind of Cupid, who himself bewilders the minds of ordinary people.

For sadhakas, when our attempts for pleasing Krishna reach the boiling point, then Krishna may reciprocate in a very special way. It may be by either showing our very fallen condition, or by revealing to us a momentary glimpse of spiritual bliss, or by taking away the multitudes of cravings and desires present in our heart thus making our heart peaceful.