... so, to participate, tell me: what activities or tasks ALWAYS will take you longer than expected?
Disposing of the body. At first you think all it takes is a big knife, a few bin bags and maybe a mop. But trust me, there's much more to it than that.
You have to get proper tools (chainsaw, at least), have a good deal of expertise (if you can get a butcher to do it for you, you're all set, but that's rare) and a lot of time on you hands.
And then there's all the blood. You never get rid of it completely. Just like the guilt, but at least guilt won't stain your carpet.
Legend of Grimrock, please!