Srimad Bhagavatam Canto 10, Chapter 32, Text 20

SB 10.32.20

naham tu sakhyo bhajato ’pi jantun
 bhajamy amisam anuvrtti-vrttaye
yathadhano labdha-dhane vinaste
 tac-cintayanyan nibhrto na veda
But the reason I do not immediately reciprocate the affection of living beings even when they worship Me, O gopis, is that I want to intensify their loving devotion. They then become like a poor man who has gained some wealth and then lost it, and who thus becomes so anxious about it that he can think of nothing else.
Lord Krsna states in Bhagavad-gita, ye yatha mam prapadyante tams tathaiva bhajamy aham: “As people approach Me, I reciprocate with them accordingly.” Yet even if the Lord is approached by someone with devotion, to intensify the devotee’s love the Lord may not immediately reciprocate fully. In fact, the Lord is truly reciprocating. After all, a sincere devotee always prays to the Lord, “Please help me to love You purely.” Therefore the Lord’s so-called neglect is actually the fulfillment of the devotee’s prayer. Lord Krsna intensifies our love for Him by apparently separating Himself from us, and the result is that we achieve what we really wanted and prayed for: intense love for the Absolute Truth, Krsna. Thus Lord Krsna’s apparent negligence is actually His thoughtful reciprocation and the fulfillment of our deepest and purest desire.
According to the acaryas, as Lord Krsna began to speak this verse the gopis looked at one another with squinting eyes, trying to hide the smiles breaking out on their faces. Even as Lord Krsna was speaking, the gopis had begun to realize that He was bringing them to the highest perfection of loving service.
Srimad Bhagavatam Canto 10, Chapter 32, Text 19
Srimad Bhagavatam Canto 10, Chapter 32, Text 21