The truth is : People don't like the idea of anyone being happier/more secure than your average Joe or Joanne.
If someone tells you about their new love of vegetarianism, we naturally worry that they are doing something better than what we're doing. And that threatens us.
We like people to do what we do, because it's likely to give them the same results that we have. We feel crap (we all do - we're humans), so at least if everyone else does what we do, they'll all feel just as crap, which makes us feel less crap.
Think about the person who's always been 'fat'. They start to lose weight, and why do people tell them to stop, or just become bitchy, or just suddenly have an opinion. Because it makes them feel worse seeing someone do something that may make them happy.
They start to doubt the things that they do differently.