Last year I wanted chicks, and hadn't yet been here. I bought Cornish X's from a chain feed store, and had no idea that they weren't going to live to become egg layers. When they were a couple of weeks old, they were out of the feed I bought, so I went to a local, non-chain feed store, and was enlightened there.
My family has often raised animals for food, but because I had got these with the intention of keeping them as pets and possibly having eggs, I had a hard time doing the dirty work myself. To that end, I gave the chicks to my brother at about 5 weeks old, and he did the dirty work and then offered me some of the cleaned freezer-ready chicken back.
I am now raising pigs, and though I'm friendly enough and pet them when I feed them, I know they're dinner, and won't have the same problem I did with the chicks.
Hopefully if you go into it knowing they're for meat, it'll be easier to seperate them in your mind from your pets.