The Grass Is Always greener On The Other Side

"The grass is always greener on the other side," this is an expression which basically means that people tend to look at others' lives and think that others' are better, until they actually feel the negative things. I think this is true, at least for me. When I was young I used to be jealous at my sister all the time, and thinking that it is unfair why this is this, that is that. My parents tried to treat us equally, but there were somethings that just can't be equal. For example, I remembered that when I was about five years old, my grandmother gave me a penguin doll and my sister a teddy bear. When I looked at my sister's teddy bear, I was jealous, because I wanted the teddy bear too. I started to complain that It was not fair why i got a penguin, but she go a teddy bear. 
Even though I know that I would still complain if I got the teddy bear instead of the penguin, because I always think the my sister's things are better than mine. This is how people look at others lives, other people's lives are always better than ours.