I am sometimes too busy or too tired and for whatever reason, I tend to miss replying to people's texts, especially if it's non-work-related. I also juggle several instant messaging applications, so moving between them can be a chore.
Unfortunately, this could go on for weeks and months without me noticing as the message thread sinks further down. When I try to reread what messages I might have missed, I noticed that some of them have not been replied to for some weeks/months, leaving the person asking a question hanging.
I know this is rude, and this is a habit I would like to kick (an entirely separate question). The problem is, if I'm actually interested in the conversation or person and would like to continue talking to them, what would be the best or most tactful way to gratefully apologize or acknowledge and move forward?