Turn it off.
Two weeks ago, I whittled it down to less than 10 messages, and today it is back up to 59, of which 30 require either an answer or some action on my part. Of the 30, 3 are personal emails from long-lost colleagues or friends who have written in the last 2 weeks. Those should be happy emails to answer, but somehow, since I don’t have time, they lay there, marked “unread” and give me fits.
I have the same problem, and periodically just sit and read/respond/delete. My Inbox currently has 249, even though I know I can axe a lot of those really old ones.