Change that burns you out in three weeks loses to change you can keep up for three years.

A pace you cannot hold is a pace that ends, and what replaces it is usually worse than where you started because now the whole idea feels like something you already failed. Intensity is easy to summon for a fortnight. Sustainability is the only property that actually determines outcomes.

Design the version of your plan you could still do on a bad week, and make that the baseline rather than the ambitious version. If you are ahead, you can always do more. What you must not do is build a routine that assumes every week is a good one.