Completion is decided by what happens when it goes wrong
Everybody manages the first month. What separates people who finish from people who do not is whether their arrangement survives an interruption.
Most people who enrol in study alongside work start well. The first weeks are manageable because motivation is high and nothing has yet gone wrong. Then something does: a period of overtime, a child who is unwell for a fortnight, a family situation, a move, an illness. Two or three weeks pass with nothing done, and at that point the outcome is largely decided, not by how much was missed but by what happens next.
Two people in identical positions diverge here. One has a way back in: they know exactly where they were, the next task is small enough to attempt while still tired, and nothing needs reconstructing. They lose a fortnight and continue. The other opens the course, cannot remember where they were, sees an assessment due in nine days, feels the accumulated weight of it, and closes the tab. The second person does not usually decide to withdraw. They defer the decision repeatedly until it is made for them.
This is why advice built around motivation and discipline misses. The people who do not finish are not less committed; almost everybody studying part-time alongside work is highly motivated, since nobody does this casually. What differs is whether the arrangement was built to absorb an interruption, and interruptions are certain rather than possible over a course lasting a year or more.
Building for that changes several ordinary decisions. It argues for shorter working sessions, because a habit requiring a clear two-hour block cannot be maintained when the block disappears, whereas one built on forty minutes survives. It argues for always stopping mid-task rather than at a natural end, because an unfinished sentence is far easier to resume than a blank page. It argues for keeping a visible note of exactly where you were, because reconstructing that is the largest part of the re-entry cost.
It also argues for front-loading. Work done ahead of schedule is the only genuine insurance available, and it is worth more than the same hours spent later, because it converts a future crisis from a failure into a delay. People who are consistently a week ahead finish; people running to the deadline are one interruption from being behind.
The second thing that decides outcomes is whether anybody knows you are doing it. Study conducted privately, fitted into gaps nobody else can see, produces a person who is exhausted for reasons their household has not been told about, and whose absence at the point of difficulty is noticed by no one. Telling people, and asking for something specific, converts a private struggle into an arrangement other people are part of.
None of this makes it easy, and it would be dishonest to suggest that the right technique makes studying alongside full-time work and caring responsibilities comfortable. It is genuinely hard and the people who do it are doing something difficult under real constraints. The claim here is narrower: that a substantial share of non-completion is a design problem rather than a personal failing, and design problems can be worked on.
A final observation about what providers could do and mostly do not. Almost everything described here is within a provider's control rather than the student's: shorter assessable units, materials that can be worked through in fragments, clear signposting of where you were, realistic guidance on hours, and extension provisions that are easy to find and easy to use. Part-time distance students are frequently a provider's most motivated cohort and the one served by materials designed for somebody else, and the completion figures reflect the design rather than the students.