A logged mistake doesn't do anything on its own. It's worth exactly nothing until it changes what you open your next study session to work on — and a lot of otherwise well-kept error logs never make that jump, because turning rows into a plan takes a different set of steps than logging does.
Wait until you have enough data
Don't build a study plan off one practice test. Five or six mistakes in a category could be chance — a bad day, an unfamiliar passage topic. Three or four weeks of logged mistakes, or two full practice tests, is usually enough to tell a real pattern from noise.
Step 1: Rank categories by mistake count, not gut feeling
Group your logged mistakes by category (not just subject — "Algebra: linear equations," not just "Math") and count them. Most students carry a gut feeling about their weak spot that turns out to be wrong once they actually count; the category with the most rows is frequently not the one they would have named from memory.
Step 2: Filter the top category by error type
Once you know your highest-count category, look at the error type breakdown within just that category. A category dominated by Knowledge Gap or Concept Misunderstanding needs actual content review — watch a lesson, read a rules summary, work untimed practice problems. A category dominated by Careless / Execution Error or Time Management doesn't need more content review at all; it needs timed practice reps and a checking habit. Studying content for a speed problem wastes the time you put into it.
Step 3: Assign it real study time, not a vague intention
"Work on geometry" isn't a plan. "Two 25-minute untimed problem sets on circle theorems, Tuesday and Thursday" is. Put it on the same calendar or schedule you use for everything else — a study plan that lives only in the error log doesn't compete well against everything else asking for your time.
Step 4: Re-test the same category before moving to the next
After a study block aimed at one category, look specifically for that category's error count on your next practice test before declaring it fixed and moving to the next weak spot. If the count dropped, you're done there for now. If it didn't, the studying you did wasn't the right kind — go back to step 2 and re-check whether you fixed a content gap that was actually a speed problem, or vice versa.
Repeat on a cycle, not once
This isn't a one-time exercise before a single test — it's a loop you run every couple of weeks: log, rank, study the top category, re-test, repeat. Each cycle should move a different category to the top of the list as the previous top one improves. If the same category stays on top after two full cycles, that's the strongest signal you'll get that something about how you're studying it isn't working, and it's worth changing approach rather than repeating the same study block a third time.
If you haven't built the underlying habit of logging and reviewing yet, start with how to start an error log and the 15-minute weekly review — this plan only works on top of a log that's actually being kept.