On Janmashtami, Krishna entered the material world at midnight. This is significant. Midnight is the time of maximum darkness and from the moment Krishna appeared, darkness started diminishing. Similarly, our heart is dark being afflicted by multiple anxieties and miseries. But in the darkest hour of our lives, when we turn to Krishna, he appears in our heart, and all the darkness recedes and the light of eternal hope starts streaming in. Krishna appeared in a prison cell and freed His parents of their shackles.
This indicates that all of us who are shackled by our own self-destructive desires can be freed by Krishna who appears in our hearts obscured in darkness.