Going insane in the brain!
Well, the best way will always be the puzzles 
...that is the key of the wcc maps: you need to go using the cube in several puzzles to get through the map until the very end of it.
This is super important. The insanity is only being used because the cube needs to travel with the player through out the chambers. During normal gameplay (Basically not what I am doing.) there should be no issues with having the cube. You just need to build the relationship with the cube. Placing the player in a simple, empty environment will help a lot.
Another good subtle way to do this is to draw attention to the cube by making in brighter than the rest of the world. You can use color correction to de-saturate all colors except pink. This will make the hearts show brighter than the world. You'd use the Selected HSV for do this.
http://www.tophattwaffle.com/ - My site for Source Engine Level Design
http://therewillbescience.com/ - Portal 2, Lab Rat
http://www.moddb.com/mods/portal-2-lab-rat - Portal 2, Lab Rat (MODDB)
Well, the best way will always be the puzzles ...that is the key of the wcc maps: you need to go using the cube in several puzzles to get through the map until the very end of it.
I forgot to mention that for the most of the time player will travel through BTS area. Maybe I can try something similar to Portal 2 where you can't drop Wheatley, but I think that restricts the player a lot.
@TopHATTwaffle: I don't know if adding a time limit is a good idea, I'd rather increase the amount of "insanity effects" to the point where you can't progress farther.
My workshop
How to control other people
[spoiler]LOL, I've just forced you to click on the 'SHOW' button! Now click here: http://soundcloud.com/vojtasiman/[/spoiler]
Something like a breakdown, you start to hallucinate, and after a few moments you faints.
