Imagine writing down your thought on the palm of your hand (you don’t have to actually write it as long as you know it is there). Then bring your hand close to your face. In that posture, it is hard to see anything else-even your hand and the thought written on it in imagination are hard to see. This is a physical metaphor for fusion: thought dominating over your awareness.
Now move your hand with the thought still on it straight out away from your face. It is a bit easier to see other things in addition to your hand. Now move your hand with the thought on it just a little to the side so you can focus on it if you need to but you can also see ahead clearly. Those actions simulate the stance you want to establish toward your thoughts. Whenever you catch yourself being dominated by a thought, note how close to you it is. Is it like that hand in your face, or off to the side? If it is in your face, see if you can move it off to the side. Note that you do not get rid of the thought this way-in fact, you see it as a thought even more clearly. But in this posture you can do many other things as well, which is the core point of defusion.