Come 17:30 work ceases to exist to me and my normal life takes over. I work to live, not vice versa. It saddens me this isn't the way for most.
The workplace started this game of paying for my time and they're getting what they paid for and not one second more.
I must say, it's worked out rather well. The suckers who make themselves available all the time at the drop of a hat get abused and certainly don't get any respect or extra thanks for it.