So using Cocktail is going to screw things up?
If you don't watch what you're doing. Things like removing languages.
You can take this however you all want, I'm not a know it all though I act like one. Cocktail has a lot of buttons to click and stuff, but I never do any of that sh¡t as routine maintenance, only troubleshooting.
The other things it offers, meh. The OS takes care of itself. The only thing I may do every 6 months or so is clean my caches. I can't remember the last time I even did it.http://www.northernsoftworks.com/elcapitancachecleaner.html
It has some possibly handy, and some possibly dangerous stuff. In Interface for example, I've heard where showing invisible files then hiding doesn't alway hide them all again for instance. Also if one doesn't know what they're doing you should stay away from things like that.