A lot of whether a day goes to plan is settled in the first few seconds after you wake, before your feet are on the floor. You remember what today is meant to be, your mind runs the whole thing at speed, and you come out the other side either committed or already looking for the exit. Understanding that quick negotiation, and stacking it in your favour, is most of what the warm-up phase is for.
The negotiation, spelled out
It runs roughly like this. If I do this today, I will be hungry. Hungry puts me in a bad mood. I will have to talk myself out of food over and over, all day, and win every time. I will sleep badly because of it, so tomorrow starts worse. On top of that I have to log everything and get the long walk in, in the heat or the cold, and I cannot push it to the evening because I am busy. By the end of that run-through, ten seconds at most, you have tipped one way or the other. The decision is rarely a grand act of will. It is this quick sum, done half-asleep.
Why willpower loses it on its own
The reason this is worth knowing is that the old way of eating has years of practice behind it and the new plan has days. Left as a fair fight, first thing in the morning, with no preparation, the practised pattern usually wins, because every objection it raises goes unanswered. Willpower tries to brute-force the same decision every morning and runs out, because there are dozens of these small decisions a day and the supply is finite.
What the warm-up does
The warm-up phase is where you load the answers in advance, so each objection meets a reply you have already worked out. Yes, you will be hungry, but you have done it before and it passed. Yes, the walk is long, but you can log on your phone as you walk and listen to something. Yes, it is hard, but two weeks of it puts you into the clothes you want to wear. The objections still come; they just no longer arrive to silence. You have stacked the other side of the table.
What "ready" really means
This reframes the vague idea of waiting to feel ready. Ready is less a mood that turns up one morning and more the morning when you have gathered enough answered objections and concrete reasons that the quick sum finally comes out in favour of getting up and starting. You can build toward that on purpose, which is the whole point of warming up before the real work.