Is this grammatically correct? What does it mean? Any possible rephrasing? Like they say “too much of everything is not good” Being too obsessive and possessive might be unhealthy for your relationship

Yes, the sentence is grammatically correct. It conveys the meaning that although one might feel strongly about something (like love or attachment), being overly obsessive and possessive can have negative effects on a romantic relationship. Here's a possible rephrasing: "As the saying goes, 'too much of anything is bad.' Being excessively obsessive and possessive can be detrimental to your relationship." This retains the original meaning while using slightly different wording.