Small pockets of time, the ten or fifteen minutes between classes, in transport, or while waiting, add up to a surprising amount over a week, and using even some of them well can lighten your bigger study sessions. The trick is to keep quick, ready tasks that fit into short gaps.
Good uses for small gaps include reviewing flashcards, reading over a page of notes, memorising a few formulas or definitions, planning your next study block, or quickly testing yourself on something you learned earlier. These bite sized reviews are actually powerful, because revisiting material in short spaced moments helps it stick far better than one long cram. Keeping a small set of flashcards or notes on your phone or in your bag means you always have something ready.
That said, you do not need to fill every free minute, and you should not try to. Rest, a short walk, or simply doing nothing for a few minutes is genuinely useful for your mind and prevents burnout. The goal is not to be productive every waking second, it is to catch a few of those gaps for light review so your main study time feels easier. Choose intentionally, use some pockets for quick revision and leave others for rest, rather than either wasting them all or grinding through every one.
Example: Reviewing ten flashcards while waiting for the bus, a few times a day, can quietly cement a whole topic without any extra sit down study time.
One practical tip: Keep a small deck of flashcards or key notes handy at all times. Short reviews in spare minutes beat one long cram for memory.