A set $X$ is said to be seperated $\iff$ $\exists$ two subsets $A $ and $ B $ of $X$ such that $A \cap cl(B) \neq \emptyset $, $B \cap cl(A) \neq \emptyset$ and $A \cup B =X$.
Now,we do not claim $cl(A) \cap cl(B) \neq \emptyset $. Does this mean that, if there are two sequences each of them in two separated sets then they may converge to the same limit point.
This is possible. Consider the sets $ (-1,0) $ and $ (0,1) $. These sets are separated, but we see that the sequences $ \{\frac{1}{n}\}_{n\geq 1} $ and $ \{-\frac{1}{n}\}_{n\geq 1} $ both converge to $ 0 $.