Rabbi Janai and Rabbi Johanan sat watching two men leave the study house. They knew something about these men that the men did not know about themselves. Two astrologers had predicted that a snake would kill both of them on that very day.
The rabbis did not warn them. They did not send them home. They simply watched.
At evening the two men returned, unharmed. Gaster's Exempla (1924), No. 172, gives no further details — only the conclusion the rabbis drew. "No astrology is of any avail against Jews."
The teaching is not that the stars carry no information. The rabbis were comfortable admitting that Gentile astrologers often read the sky with technical accuracy. The teaching is that a Jew stands in a different relationship to the decree. Through Torah, through the mitzvot, through giving a coin to the poor at the right moment, a Jew can reroute what the stars had written. The Talmud elsewhere (Shabbat 156a) frames it in a line: ein mazal l'Yisrael — Israel has no constellation.
A snake may be written into your chart. A blessing recited over bread may be written deeper.