Short answer: Record every mistake with its reason and review the log weekly.
What to record
Question, correct answer and the reason you missed it.
Review weekly
Group errors by type and revisit weak topics.
Retest
Redo the questions after a few days.
Frequently asked questions
What format works?
A notebook or spreadsheet, whichever you will use daily.
How long should it take?
A few minutes per test.