Each day is a new chance for positivity, and today I will be positive.

A shop opens at nine whatever yesterday's takings were. The till gets counted, the float goes back in, and the first customer of the morning has no idea what Thursday was like.

Days work a bit like that, though not completely — you carry in some of yesterday's residue, in your back and in your inbox. What's genuinely new is the unspent part. Nothing between now and six has happened yet, and that isn't a small quantity of room.

Promising the day in advance is a strange act: made to nobody, with no enforcement attached. It works anyway, more often than it should, probably because the promise gets remembered around four in the afternoon at exactly the moment it's needed.