Prabhupada said:“Lord Krishna is acyuta – he is infallible. Acyuta – being infallible he will never fall down!”
But the living entity is potentially a spark – Krishna is fire and the living being is like spark. So a spark due to its insignificance, when it is in contact with the fire will also burn like fire! But, when it is not in contact with the fire then it will no longer burn like fire and will become extinguished. So, potentially the living being can extinguish its natural Krishna Conscious