Soul #1 is a switch flipper. In other words, his love, attention, respect, flips on like a switch. He flits all over the place constantly in search of something new and exciting. He is unable to develop his own inner light. He hops from relationship to relationship as a way to sustain his life force. The kicker is that he cannot communicate in a healthy manner. He chooses to play games instead. Now, eventually this game playing makes him feel empty and when this occurs he sets up house with Soul #2.
Now, that Soul #2 has made the pledge to never take him back. He is feeling out of sorts and looking for a stable place to land after his current relationship goes off the rails. He doesn't see anything wrong with how he is treating her. Soul #1 does want a life long relationship with Soul #2 but, lacks the maturity to do so.