The words power, concentrate, and attention, imply doing and effort. To meditate and to be able to go deep into the still, calm, peaceful space within us we need to get into an effortless space of non-doing being. To witness all that is arising in the moment without seeking to engage with any of it. Thoughts would keep on arising and we simply witness these thoughts and choose not to react or respond. This includes not blocking the thoughts and simply allowing them to rise and flow, not holding on to the thought, not following the thought and not getting carried away by the thought. We remain unswayed, a witness to all arising phenomena.
Initially when our mind is very restless, it is almost impossible to sit merely as a witness in this way. That is the time when we hold on to something and this is called shifting into our grounding connection.
The following article and all the linked articles therein may help to practice and experience deep calmness.