It is probably not a far-fetched idea that we all have hidden pain inside our hearts and minds. Often, part of any relationship-building experience is learning that OUR emotional pain is ours alone. And the harder lesson: the emotional pain of our partners is most definitely NOT OURS.
“Stay in your lane” means learning to support your partner when they are in pain, but not to take that pain on as yours to solve. We cannot solve the emotional pain of our partners. What we can do is stand strong beside them, assure them that we are listening and empathetic, and then be quiet and let them tell us what they need. Often, what they need may not involve you or your input.