If we shake our hand in front of our face we will not see its shape, as there is no stability or clarity. But the less it shakes, the more of it we can see. Likewise, it is impossible for our mind to experience great results on the buddhist path if it has continuous agitation and dullness. The less agitation and dullness, the greater the stability and clarity, therefore the more power the mind has during any meditation on the path, whether sutra, tantra, or dzogchen.

-- Chamtrul Rinpoche