the power of now was a good book on this. there are many other great books.
I like to think of it as here i am and there my mind is. all my thoughts emotions etc.. are all transient coming and going rising and falling. Its best if i be the watcher on the wall of all of this coming and going rather then getting all attached to all of that. If i'm not careful my mind can drag me around by the nose whereever it wishes.
various situations can really suck you in however but just dont take the bait dont bite the hook just observe.