Sacred Haven of Debauchery

So, I’m walking from the kitchen to the bathroom, with a knife in my hand. I see a colleague coming in, and suddenly I have this random thought – I could stab him hard in the stomach, right to the spine, this fat guy. I even pictured it in detail, with what trajectory, how it would first tear through his jacket, get slightly caught in his undershirt, then cut through the fat... The knife is sturdy, all-metal, with a blade over 20 cm long. Well, I think, I won’t do it this time. I’m already in the bathroom, washing the knife, and he comes in to wash his hands, and then he says:
-- Hey... You were going to stab me with that knife, right?
I’m a little shocked, but I was taught that lying is bad.
-- Well, yes, how did you guess?!
-- Well, we’ve known each other for a while...