CleanMyMac?

All cleaning applications aren't good for your Mac. They sometimes delete wrong files, making OS X unusable, and they doesn't work properly. Furthermore, some of them are considered as malware, like MacKeeper.

Don't install it. OS X knows how to take care of itself, and it runs maintenance scripts to keep your Mac working correctly > http://pondini.org/OSX/Scripts.html

Some Links to amplify Mende1's advice.

https://discussions.apple.com/docs/DOC-3691

https://discussions.apple.com/thread/3864298

Avoid CleanMyMac... avoid all third party cleaning utillities.

Your Mac runs background maintenance for you.

Mac OS X: About background maintenance tasks