A sustainable routine knows what minimum effort looks like.

Every routine you intend to keep for years needs a floor, a version so small that no circumstance can honestly excuse skipping it. Without a floor, the only options are full effort or nothing, and on the days when full effort is impossible you get nothing by default. The floor is what keeps the chain intact.

Decide what your five-minute version is and write it somewhere you will see it. Make it genuinely small, small enough to feel almost silly. Its purpose is not progress on hard days. Its purpose is continuity.