Why do my thoughts fade away when I watch them during meditation?

Certainly, what you're experiencing is quite common and actually a sign of progress in meditation practice. When you observe your thoughts with detached awareness during meditation, you're essentially creating a space of non-engagement. By not getting entangled in the stories or emotions associated with your thoughts, you're not fueling them with energy, and as a result, they naturally begin to lose their power and fade away. 

Think of your thoughts like clouds passing through the sky of your mind. When you don't attach yourself to them or follow them down the rabbit hole of rumination, they simply drift by without leaving a lasting impact. Similarly, when you observe your thoughts without judgment or attachment, you're creating a mental environment where they can arise and dissipate without causing disturbance. 

So, the fact that your thoughts disappear as you watch them is actually a positive sign that you're practicing mindfulness effectively. It indicates that you're developing the ability to observe the contents of your mind with clarity and equanimity, without getting swept away by them. 

Remember, meditation is not about suppressing or controlling your thoughts but rather about developing a spacious awareness that allows thoughts to come and go naturally. It's a skill that requires patience, practice, and persistence.