I use external monitors all the time with my MacBook. I’ve mentioned before that I don’t think OSX Mavericks doesn’t really handle them as well as it could. I’ve come to discover an additional problem with utilizing external monitors. Sometimes, when you disconnect your monitor from your MacBook, OSX will not detect that the monitor has been disconnected.
If you have this problem with OSX and it is not detecting the monitor configuration change, then execute the following keyboard shortcut:
I hope that helps!