Units should be designed such that instructions, expectations, and time management for completion are so clear that there are layers of safety nets so that even if a student fails, misses, or does not meet expectations in certain steps, they still have opportunity to get instant timely feedback and guided to continue succeeding.
Summative assessments are benchmarks. (the Game)
Formative assessments and daily feedback from students fills in the gaps between summative assessments, helps to show students how much they understand, and helps to inform teacher judgment in assigning final grades. (the Practice)
Learning is continual process of improvement and betterment ... it is meant to be a struggle for achievement ... and to quote a colleague, it is like an 'asymptote' which we can always strive to reach, and we can approach, but never actually reach or cross.