1
Day one.
One day is enough to start. There is no perfect time. Whatever brought you here is enough.
What might come up
Anticipation. Doubt. The urge to celebrate the decision by breaking it. The urge to dismiss the decision as not a big deal. None of these reactions mean anything is wrong. They are common, they pass, and the counter does not care about any of them. It only counts forward.
What changes today
The count starts. The data starts. A choice that was abstract becomes a number you can point to. The first time you check the counter and see a one is a small but durable thing.
People come to day one for different reasons. There is no template for what it should feel like.