I like to try to see mind like a crystal pool of water..Effervescent water.
During meditation thoughts will just pop in and tend to draw your focus away from breath.
This is like the bubbles that rise though the water and imagine each bubble akin to a thought.
See thought arising and it kind of just manifests in your mind when the bubble surfaces.
The point in Shamantha (Breath) meditation is to train our mind to become like clear still water with no effordesance or bubbles. When we experience complete stillness it sort of gives your mind a rest and things become clearer and we live more appropriately. When we sleep we really are just resting the mind a small amount because we dream and work things out in our sleep.
I am going to share a technique I have worked out with Yoga and meditation....a sort of trick to help your mind settle into that "No-thought~Clear-water state".
I sit down and do this (see link) for about 1-2 minutes.
Then I take my index finger and place it in the divet where you spine goes into your skull and put some pressure for 30 to 60 seconds (not hard pressure but some).
Now I go into my meditation posture and begin meditation. ~Namaste'