As I have often said in these blogs and in other writings of mine, mindfulness is not about silencing or stopping thoughts but rather developing a new and altogether different ‘relationship’ with your thoughts. Instead of grasping, chasing after, or clinging to thoughts, you simply observe. That means, among things, that you not identify with any thoughts as they arise ... and they will! If you identify with any thought, you give it power and intensity. You know that to be true from past experience.
As soon as you recognise that your mind is restless or wandering, ‘note’ that fact. Then you can simply observe the mind as it ‘plays itself out,’ so to speak. By simply accepting the restless or wandering mind as it is, without expecting thoughts to stop (let alone trying to stop them – heaven forbid!), and practising observation and choiceless awareness, the thoughts will slow down. They may even stop altogether.
Killingsworth, M A, and Gilbert, D T. ‘A Wandering Mind is an Unhappy Mind’, Science, 330: 6006, 12 November 2010: 932. DOI:10.1126/science.1192439.
Mason, M F, et al. ‘Wandering Minds: The Default Network and Stimulus-Independent Thought’, Science, 315: 5810, 9 January 2007: 393-395. DOI:10.1126/science.1131295.