It's funny the things you remember from your childhood -- often it's not the big events that stick in your memory, but the small, silly little things. I remember breakfast time. Specifically, I remember the Battle of the Toast.
You see, every morning my mom would toast up and butter a big old stack of toast and put it on the breakfast table. Right in the middle of the table. I had two older brothers, and the Battle of the Toast was a war to see who would get the most toast for breakfast. It was a silly thing; none of us needed more than a couple slices of toast with jam or peanut butter, but none of us ever thought about what we needed, or even what we wanted. Instead we only thought about what "the other guy" was getting. And our desires were defined by what "the other guy" had. Thus, if my brother ate four pieces of toast, then I just had to have four pieces of toast. Didn't matter if I was already full; I had to keep up.
Eventually, Mom put a stop to the Battle of the Toast by carefully counting out how many slices of bread she toasted, and limiting us to two slices apiece. Seems kind of silly now, doesn't it?
But this is the cost of envy -- the cost of looking at the other person and comparing what I have to what they have. I stop thinking about what is good (or even what is healthy) and I just have to have what they have. It makes no difference if I need it, makes no difference if it is good for me. I want it.
Just like Peter tells us to put aside deceit, malice, hypocrisy, and slander, he also tells us (1 Peter 2:1) to put aside envy. Envy is the mentality behind the Battle of the Toast -- it is the desire for what someone else has. And we will never be healthy as long as we measure our life and our possessions in comparison to what someone else has.