Repetition is the point

Practice

All of this rewards doing it badly at first. Twenty minutes a night for a week beats three hours the day before, and that is not a motivational line, it is how the spacing works.

The cards come back on their own. A card you get right returns in a few days, then a week, then three. A card you miss comes back tomorrow, and again before you leave. So a sitting is short and it ends: the due count goes to zero and the page says so. New cards are never pushed at you. Miss a week and nothing is lost or broken, there are simply more waiting. None of it leaves your browser.