The Trap of Trying Not To Think
Trying hard to suppress a specific thought often makes it pop into your head even more. By fighting to ignore an idea, you accidentally force your brain to check if you are still thinking about it.
This phenomenon is known as the white bear problem because trying to ignore the image of a white bear usually makes it impossible to forget. It happens because your brain must constantly monitor for the forbidden thought to ensure it stays away. This subconscious check keeps the topic active in your mind, causing a rebound effect. It explains why we often struggle to stop worrying or obsessing over things we want to leave behind.
Source: Ironic process theory