Build habits that bend instead of shatter.

Rigidity looks like seriousness and behaves like fragility. A habit with only one acceptable form has to break the first time that form is unavailable, and once broken it usually stays broken because there is no partial version to fall back on. Bending is not a weakening of the standard. It is what gives the standard somewhere to go under pressure.

Define two or three legitimate sizes for the thing you are trying to sustain: full, reduced, and minimal. Then difficult days have a move available that is not stopping.