In plain words
The moonlight grows day by day, and on the full-moon day its beauty reaches its height. In the same way, as man's mind blossoms, there is the chance for man himself to become Mādhava, step by step. So we must develop the blossoming of the mind step by step. We must make the mind broad. But today that is not happening. Letting the narrow feelings of 'one's own' and 'another's' into his mind, man is making his heart small.
The heart is very vast. It must not be confined to the narrow feelings of 'I' and 'my people'. Everyone needs pure Prema and a broad heart. Thieves have entered the house and are behaving like its lords. The very moment people recognise that they are thieves and not lords, they run away. We are keeping the thieves as though they were lords. We take them for the masters of the house. They are not the masters. These thieves are kāma, krodha, lobha, moha, mada and mātsarya. Taken all together, in Vedānta they go by the name 'the three obstacles'.
The obstacle of the past
Man is bound by three kinds of obstacles. One is the obstacle of the past, the second the obstacle of the present, the third the obstacle of the future. What is the obstacle of the past? In a village there lived a poor family man. He got a cow, sold its milk and kept his family with great hardship. After some time his family died. For some time he grieved. Then the cow too, which he had reared and fed with such love, died.