Sometimes we want to let go of painful things but contrary to our wishes, those memories get stuck in our minds. This may happen because we keep associating them with a set of strong difficult emotions. Learning to enter in contact with them, avoiding any type of reactivity, or desire to make them disappear, is key to letting them go.
In this case, acceptance, curiosity, and willingness to understand what they are trying to teach us, things will help them to get unstuck and follow their path.
The aim of this exercise is to practice approaching those things with serenity, curiosity, and compassion, so they lose their emotional power over us.