The feeling will pass without help
The flicker
The next three chapters are the method. This one is about the first thirty seconds, which is where the whole thing is decided.
Catch it. The flicker has a body signature and you can learn yours. For most people it's a slackening in the chest, or a tightening in the jaw, or a restlessness in the hands, or the eyes going to the drawer or the phone before the mind has caught up. Find yours by watching for a day. Once you know it, you have a few seconds between the flicker and the hand, and those seconds are the method.
Name it. One word, said in your head or under your breath. Bored. Flat. Awkward. Tense. Sad. Restless. Lonely. Kircanski's spider study is the evidence that putting a feeling into words does something to it that distraction doesn't, and the word is the first thing the remedy has always prevented. If the first word that comes is "hungry", check it. Would an apple do? If not, it wasn't hunger.
Score it. Out of ten. This takes two seconds and does two jobs. It tells you what you're dealing with, and it turns a formless discomfort into a number, which is a smaller thing than a formless discomfort. Most scores will be twos and threes. A seven is chapter 14.
Say the sentence. "This will pass without help." It's the title of the book and it's the thing you've never once tested. Say it as a prediction, not a hope. Then test it.
Ten minutes. Set a timer if you like. Carry on with what you were doing. Don't reach. Don't fight the feeling either. Just let it be there while you do the next thing. At ten minutes, score it again.
Then decide. If the score has fallen, which is what I'd expect most of the time, there's nothing to decide. The wave passed and you watched it. If it hasn't, ask whether there's a second word behind the first, and go to chapter 20. And if after all that you still want the biscuit, have the biscuit. It's now a choice made at the end of a wave, not a reach made at the start of one, and that's the whole difference.
One word on paper. In the first week, write the word and the two scores down each time. A list of "flat 3, 1" and "bored 2, 0" and "tense 4, 2" is the most persuasive document you'll ever read about yourself, because it's your own evidence that the feeling passes without help.