In practice, some come to see easily, some with difficulty. But whatever the case, never mind. Difficult or easy, the Buddha said not to be heedless. Just that--don't be heedless. Why? Because life is not certain. Wherever we start to think that things are certain, uncertainty is lurking right there. Heedlessness is just holding things as certain. It is grasping at certainty where there is no certainty and looking for truth in things that are not true. Be careful! They are likely to bite you sometime in the future!
Source: Being Dharma : The Essence of the Buddha's Teachings