Click the "Manage your schedules" link underneath your list of schedules on the dashboard, and click "Freeze" next to whichever schedules you'd like to freeze.
Or, go to the settings for your schedule, click "More settings" at the bottom of the pop-up, click "Advanced settings", and scroll to the bottom for the Freeze button.
You can also freeze your whole account at once by going to your user settings and using the "Freeze my account" button.
What @gillianfaith said. Additionally, you can set schedules to "Review" mode. You can also change the amount of new terms you learn daily. Just letting you know so you don't end up in the same situation :)
