When attachment does not arise, grasping or upadana will not arise. When grasping does not arise, there will not be any wholesome or unwholesome actions, verbal, physical or mental. The action that is caused by grasping is known as kamma bhava. This may be wholesome or unwholesome. Wholesome bodily action is kusala kaya kamma. Unwholesome bodily action is akusala kaya kamma. Wholesome verbal action is kusala vaci kamma. Unwholesome verbal action akusala vaci kamma. Wholesome mental action is kusala mano kamma. Unwholesome mental action is akusala mano kamma. These actions or kamma arise through the grasping which is the result of attachment to pleasant or unpleasant feeling or sensation.
When any bodily, verbal or mental action is carried out, it becomes a cause. This cause has its result which may occur in this life, or future lives. So in this way, a being is reborn again through his wholesome or unwholesome action. That action is caused by the grasping which has attachment as its root. Attachment, in turn, is conditioned through reeling or sensation, vedana In this way, a being has to be reborn in the next existence to experience a variety of suffering because he does not observe his pleasant feelings together with his experience.
Therefore, if a meditator thinks that feelings should not be observed, he will be carried away along the Chain of Dependent Origination (paticcasamuppada) to be reborn in the next existence and suffer from a variety of dukkha. That is why the Buddha teaches us to be mindful of any kind of feeling or sensation whether pleasant, unpleasant or neutral.