The loop is replaying the same situation over and over. Much like the children of Israel who continued to go around the mountain. The mind continues on the same thought pattern it had from previous cycles or situations until that pattern of thought is broken. Of course, we are speaking of mental loops that are not productive that need to be reviewed and released. 
Moreover, self-reflection is a process that can bring awareness to mental loops. Mental loops are again repeating themes we create in our lives. As we begin to identify the memories and behaviors that are unproductive pertaining to mental loops, we can shift these thoughts as they come in realigning our consciousness.