Without any review, most new information fades quickly — a large share of it within a day or two, and more over the following weeks. This pattern is often called the forgetting curve: forgetting isn't a rare failure, it's the default outcome of learning something once and moving on.
The good news is that each time you successfully retrieve a memory, the rate at which it fades afterward slows down. That's the idea behind spaced review: instead of studying a topic once and hoping it sticks, you revisit it a few times with gaps in between, and each pass buys you a longer stretch before the next one is needed.
A workable version of this, without any special software:
- Review new material the next day, while it's still fairly fresh.
- Review it again after about a week.
- Review it again after two to three weeks.
- After that, a monthly check-in is often enough to keep it in place.
The exact intervals matter less than the principle: short, repeated, spaced-out retrieval beats one long cram session, even when the total study time is the same. If you only have time to change one habit, moving from "study it once, hard" to "study it a few times, briefly, with gaps" is probably the highest-leverage change available.