Why waiting feels right
The wait isn't laziness, and it isn't coldness. If it were, this would be a different book. People who wait are often the most considerate people in any group. They wait because they're thinking about the other person. This chapter sets out the case for waiting as fairly as I can, because you can't change a habit whose reasons you haven't looked at.
I can find four reasons, and each has something real in it.
The first is not wanting to intrude. Your friend has a job, a family and a full week. A message from you is one more thing to answer. You picture them seeing your name, sighing slightly, and thinking they'll have to reply to that at some point. You'd hate to be a chore on someone's list. Leaving them in peace seems the kind thing to do.
The second is evidence. People do what they want to do. Your friend has had fourteen months in which a message would have taken thirty seconds. They haven't sent one. The simplest reading is that they don't especially want to. If that's so, then getting in touch would put them in the position of having to be polite to someone they've moved on from. The silence seems to be telling you something, and you're listening.
The third is fairness. You sent the last real message. In the six years of Thursdays it was usually you who said "lunch?". A friendship ought to run in both directions. If you're always the one who makes the effort, what does that say? At some point self-respect says stop, and see if they come to you.
The fourth is protection. If you message and get a warm reply, that's lovely. But you might get a cool one, or a vague one, or none. While you don't ask, you don't find out. The friendship stays in a state where it might still be fine. If you sent a message and it fell flat, the fact would be settled and you'd have to live with it. Not knowing seems the better thing to keep.
Underneath these are needs that nobody should be embarrassed about. You want to be wanted and not merely tolerated, and you don't want to be a nuisance. Your friendships should be mutual, and you'd like to avoid being hurt. Every one of those is reasonable.
What I'm going to question is whether the wait serves them. Each of the four reasons depends on a guess about what's going on in the other person's head. The first guesses that they'd find your message a burden, and the second that their silence reflects their wishes. Behind the third is a guess that they're keeping the same tally you are. The fourth guesses that a flat reply is likely and would mean what you fear.
You made all of those guesses alone, on a Sunday afternoon, with no information from your friend at all. The next five chapters take them one at a time and set them against what researchers have found when they've gone and asked the people on the other end.