Perhaps you have practised meditation or some other method of calming the mind. If so you will know that the task is not trivial. If you have not, I suggest you try now to empty your mind for a minute or so. When any thought comes along, as if certainly will, just acknowledge it and let it go. Do not get tangled up in the thoughts or follow them up. See whether you can find any space between them. The simplest forms of meditation are no more than this kind of practice. It is fiendishly difficult.
Why? You will doubtless notice that thoughts just seem to pop up of nowhere and grab your attention. You may also notice what kinds of thought they are. Typically, they are imagined conversations or arguments, reruns of events with new endings, self-justifications, complicated plans for the future, or difficult decisions that have to be made. They are rarely simple images, perceptions or feelings (which can come and go without causing trouble); rather, they use words, arguments, and ideas you have acquired from other peoples. In other words, these incessant thoughts are memes. ‘You cannot command them to cease. You cannot even command them to go slower nor tell yourself not to get sucked into them. They seem to have a life and power of their own.
Susan Blackmore