Simplify the following text for a Grade 13 native English-speaking person.
Original: Gunnysacking is a metaphor used in conflict resolution that involves the act of `` storing up '' grievances acquired in the course of a relationship without systematically resolving them .
Simplified: Gunnysacking is a metaphor , used in conflict resolution , which involves the act of `` storing up '' grievances acquired in the course of a relationship , rather than resolve them when they first occurred .