How do i Focusing on the breath and letting thought go
You should stay with the breath as much as you can. Therefore, if a thought arises &amp; it will just float away, then let the thought float away; like it is a passing visitor. 

You only have to 'let go' of something after you have 'picked it up'. Therefore, if you have not picked up (attached to) the thought, you do not need to let it go. Instead, just stay with the breathing &amp; let the thought float by &amp; away. 

This method develops both samatha (calmness) &amp; vipassana (insight).