How do I stop unintentionally Ignoring someone?

Whenever I find myself in a conversation with someone, could be anyone, even someone who I love and hold dear to me, but whenever something else happens, or someone else comes up and interrupts the previous conversation, my focus will immediately land on that new thing or person, and everything else becomes, I don’t know like blurred, or in audible and I end up “ignoring” the previous person. I don’t know why I do this, and it’s been negatively impacting all of my relationships, I just want it to stop.