Three easy steps to total despair:
1. Collect browser tabs for weeks, while working on some longer project; have them automatically recovered whenever you close and relaunch the browser.
2. Open a new browser window to have some random page on another screen or something.
3. Accidentally close the window with the bunch of tabs first, and the one with a single random tab second. Now browser will recover just that one inconsequential tab the next time it runs.