You can unregister as an instructor by going to your profile page and clicking the settings tab. At the bottom of the page you'll find the Unregister as instructor button.
Alternatively, you can also make all your skills inactive. This makes them no longer visible and disables the ability of others to book you. This way you can always continue where you left off whenever you want to.
If you do decide to unregister, you will lose all instructor related functionality and your account will become a regular customer account. We will keep you skills stored for some time in case you change your mind.
Note that you can only unregister if you don't have any pending or confirmed bookings for your skills. If this is the case, you could decline / cancel them before unregistering.
If you want to learn how to delete your account, please read this article.