Stability and difficulty

Yuhimo schedules learning pages using FSRS-light. FSRS-light uses your review grade and the page's current learning state.

Stability and difficulty are part of that state. Together with retrievability and the due date, they help decide when the page should appear again.

1. Learning page enters a review session
2. You give Again, Hard, Good, or Easy
3. Yuhimo updates scheduling state
4. The next due date changes

You interact with simple review grades. Yuhimo handles the scheduling details.

Stability represents how durable the memory is expected to be.

Higher stability usually means the page can wait longer before the next review. Lower stability usually means the page should return sooner.

Stability is based on review history, not just one review. A page that is consistently remembered well can become more stable over time.

If you repeatedly review a page and mark it Good or Easy, Yuhimo may treat that page as more stable and schedule it farther into the future.

Difficulty represents how hard the page appears to be for you to retain.

Higher difficulty usually means Yuhimo should be more careful with scheduling. Lower difficulty usually means the page is easier to keep in memory.

Difficulty can change over time as you review the page. A page can be important but still difficult. A page can be simple but still unstable if it has not been reviewed enough.

A page about a familiar concept may become easier to retain. A page with dense definitions, formulas, or many similar details may stay difficult for longer.

In the app, difficulty is shown on a 1–10 scale. Yuhimo keeps values inside that range internally when scheduling updates run.

You do not edit stability or difficulty directly. After reviews, you can inspect them in Learning statistics. Stability is expressed in days; difficulty appears as a value out of 10.

For internal scheduling bounds (such as maximum interval), see FSRS-light explained.

Each review grade sends a different signal. The exact numeric changes are internal, but the general effects are:

Again:

• means recall failed or was not good enough
• usually lowers scheduling confidence
• can reduce stability growth
• can make Yuhimo bring the page back sooner
• may increase the apparent difficulty

Hard:

• means recall succeeded but required effort
• may still move the page forward
• usually gives less progress than Good or Easy
• can signal that the page remains relatively difficult

Good:

• means recall was successful enough
• usually supports normal scheduling progress
• can increase stability in a balanced way

Easy:

• means recall was strong and quick
• may increase scheduling progress more than Good
• can signal that the page is easier to retain

These grades come from self-assessment, not automatic answer checking.

Two pages can receive different due dates even if they were reviewed on the same day.

• different review histories
• different previous grades
• different stability
• different difficulty
• early or late review timing
• failed reviews in the past
• stronger recall on one page than another

If Page A has been remembered easily several times, it may be scheduled farther out. If Page B was marked Hard or Again recently, it may come back sooner.

See Early and late reviews for how review timing also affects scheduling.

Stability is not your emotional confidence. It is an internal scheduling estimate.

You may feel unsure but still recall correctly. You may feel confident but fail to recall details.

The review grade should reflect actual recall, not how nice the topic feels. That is why Yuhimo uses self-assessment.

A high-difficulty page does not mean you are bad at learning.

It may mean the material is dense, unfamiliar, abstract, or easy to confuse. Difficult pages are normal in learning.

Yuhimo uses difficulty to avoid pushing hard material too far into the future too quickly.

• Grade honestly
• Use Again when recall fails
• Use Hard when recall works but is effortful
• Use Good for normal successful recall
• Use Easy only when recall is clearly strong
• Do not try to game stability or difficulty
• Improve the page content if it remains hard to remember
• Add questions if prompts would help recall
• Split a page if it covers too many unrelated ideas

If a page keeps feeling hard to remember, scheduling may not be the only problem. The page content may be too vague, too large, or too unstructured.

You can:

• rewrite the explanation
• add examples
• add better questions
• split the page into smaller child pages
• remove irrelevant content
• turn a messy note into a clearer learning page
• review the source material again if needed

FSRS-light explained — overview of the scheduling model.

Retrievability — how likely recall is at a given moment.

How reviews work — the review session flow.

Early and late reviews — how review timing affects scheduling.

Self-Assessment — why you choose the rating.

One grade per day — why each page gets one rating per day.

Can I manually edit stability or difficulty?

No. In the normal Yuhimo workflow, these are internal scheduling values updated from your reviews.

Does high difficulty mean I failed?

No. It means the page appears harder to retain. Difficult material is normal, especially when it is dense, new, or easy to confuse.

Does Easy always create a much longer interval?

Usually Easy gives more scheduling progress than Good, but the final due date can also depend on review history, current stability, difficulty, and timing.

Why did a page I marked Good come back soon?

Because Good is only one input. The page may still have low stability, high difficulty, limited review history, or recent failed reviews.

Can a page become easier over time?

Yes. If you repeatedly recall it well, Yuhimo may treat it as easier and more stable over time.

Should I mark everything Easy to push reviews away?

No. That weakens scheduling quality. Grades should reflect actual recall, or Yuhimo's future review timing becomes less useful.