The all-or-nothing trap
The dangerous moment is not the missed day, it is the story afterwards: "I have ruined it, I will start again properly on Monday." That story throws away weeks of accumulated practice over a single gap, and it usually delays the restart by far longer than the original lapse.
Nothing was actually deleted. The habit is still mostly built; you simply stopped for a while.
Restart smaller than you left off
The instinct after a break is to compensate: go twice as hard to make up for lost time. That almost always produces a second collapse, because you are demanding peak performance from a system that is currently cold.
Do the opposite. Restart at the minimum version, five minutes, one page, one short focus block. The goal of the first session back is not output, it is re-establishing that you are still someone who does this.
Resume today, not Monday
Waiting for a clean boundary, next Monday, next month, the first of the year, is procrastination wearing a respectable coat. Every day you wait makes restarting slightly harder and the story about your failure slightly stronger.
Do the smallest version now, today, however unimpressive. Momentum does not care that it is a Wednesday.
Make recovery part of the plan
Anyone who sustains a practice for years has fallen off many times. What separates them is not that they never break, it is that their gaps last one day instead of three months. Recovery is itself a habit you can get good at.
Decide now what your comeback looks like, so the next lapse has a pre-written ending: minimum version, same day or next, no lecture.