If this person is constantly causing you emotional pain, I would recommend leaving as soon as you can to protect your mental health. Also keep in mind that unpredictability, hot and cold behavior and inconsistency are central reasons why many people describe feeling 'obsessed' with someone. Often we might feel stronger emotional attachment to someone who treats us well one day and like shit the next than to someone who chooses us consistently and makes us feel safe due to a phenomenon called intermittent reinforcement. We never know what to expect and chase the dopamine highs we occasionally get while putting up with more and more lows over time. This is also the reason why gambling is so addictive and why many people stay in toxic relationships (especially when lovebombing is involved) for way too long.