Rumination is when your minds get stuck on certain thoughts, usually negative ones. It's like a broken record in your mind that won't stop playing. When we ruminate over the past we keep replaying certain events, worrying about things we said, overthinking our actions and wishing their was a different outcome. This can easily make you feel overwhelmed, anxious and has a detrimental impact on your mental health.
This is because it's a completed wasted energy - we can't change the past! What we can do though is anchor our minds in the present moment and tapping is a great way to do that and stop the rumination.