Thomas Brand addressed one of the most common myth on disk permissions:
The only time you need to run Repair Disk Permissions is if you changed a system-level permission you shouldn’t have.
I used to stay up late searching for tools and tips to optimize Mac. I downloaded all the some recommended applications that claim to optimize and speed up OS X. I guess what they do are simply clearing caches and changing priority of the processes. It wasn’t a pleasant experience. I ended up staying awake whole night trying to revert its condition from fast to normal.
Nowadays, I let OS X manages everything. I’ve only adjusted some animations to improve my experience.
Avoid needless hacks when OS X doesn’t freeze your Mac. Instead of spending your time to optimize OS X, try to come up with a way to finish your tasks efficiently.