An ordinary moment can become a turning point without announcing a change in direction.

Change almost never arrives with a label on it. The conversation that redirected your life looked like an ordinary conversation while it was happening. You recognise the hinge afterwards, from the far side of it, which means the days that turn out to matter are indistinguishable from the rest while you are inside them.

You cannot pick them out in advance, so the only workable answer is to give ordinary occasions a little more of yourself than they seem to require. Reply to the message. Stay for the second half of the conversation.