problem with grabbing and placing cube

Oh so my problem is i have a cube i like to move around freely in the game. I have gotten it down the final area i am having trouble with. If you grab a cube below you can jump or go off a edge and you will be free flying. Any ideas on how I can make it so the player can't grab the cube he is on by chance. I am just using the unity character controller and motor for movement and such. Any help will be greatly nice as i looked hours online and tried what they have said and nothing has helped.

 

I'm not a pro with unity but i don't really able to understand what you'v described over there...

 

in games like portal and such you can grab a cube and place it somewhere else. I want to do that. Currently i can do that but, if the player looks down and grabs the cube many bugs happens as the player can launches himself skyhigh and other stuff.

 

Without code, we have no idea as to what you are doing to get the functionality/issues you are having. One cannot analyze a black box without even the box.