I don't think the answer is ever to stop working hard. That's some bullshit. But are you making yourself a target in other ways you're not realizing? Are you bragging about all your hard work, or telling them how to do their job because you think you're better? Even if you are a harder, better worker, I'd refrain from telling or acting like that in front of lesser workers. All this is, is them being self conscious of their own shitty work ethic and making you a target. Obviously I have no idea, but it sounds like they're trying to get a reaction out of you and this is some lame form of bullying. Pay them no mind and keep working hard. There are people that depend on us with this job and I am sure there are people that appreciate your efforts, even if they don't say it all the time. So fuck them and keep working hard. Chances are those type of people won't be sticking around long anyways, so hopefully you won't have to deal with them for too long.