You should improve yourself, change yourself, and make yourself different from him every day, because only when love keeps a freshness will he focus on you and won't meet other girls, which will greatly reduce the probability of cheating. But I don't think this method is advisable, because if you really love someone, no matter what the other person is like, you may especially like them, and you will treat their feelings wholeheartedly, so you change yourself just to gain the attention of others, so you will lose yourself. I think this method is not particularly good!
Even a playboy man, if he loves you deeply, I think he will definitely consider your feelings and will not cheat; And a man who is easy to cheat and scum often shows that he doesn't really love you, so when you meet a Sagittarius boyfriend, I don't think you want to stop him from cheating. You must first determine whether there is true love between you two, and whether he really loves you; If not, he is not single-minded about your feelings, which only shows that he doesn't love you. I think you should consider ending this relationship in this situation.
Therefore, in our life, everyone will meet all kinds of boys, not to say that a scum can be judged by the horoscope alone. I think each of us should seriously choose to find someone who is really good to ourselves, so that there will be no such worry. Believe in the person who really loves you, he will not make you sad, nor will he spend his heart, but will only treat your feelings wholeheartedly.