Don't worry we've all been there. Last week I left my Facebook account logged in on a friend's phone, which is what lead me up to type up this post. There's no need to panic as the instructions are extremely easy. Using your computer you can log yourself out of any phone or computer that you left yourself logged into.
1- Log into Facebook using your computer, then tap on account settings
2- Tap on Security in the left sidebar, then edit Active Sessions
3- End a specific session to log yourself out of that device, or end all active sessions if you want to stay on the safe side. Ending all active sessions will log you out of all devices except the one you're currently using to end sessions
That's it. Your Facebook account is now safe from evil friends. How about you share this post to help your friends sleep with less worry tonight? It would mean a lot to them, and to me.