"The Grass is always greener on the other side of the fence."
I hope you also realize that it isn't "always" true.
Your neighbor may seem to have it all but you don't know what pains she goes through. Your friend with the perfect marriage? No marriage is perfect, there has to be some lows to appreciate the highs. The co-worker with the fabulous figure? Who knows what is really going on there.
You may always want to be better, stronger, richer, smarter, or safer. But, is it really so bad where you are? What can you do to improve your own? Let others motivate you, but never be envious.
Another saying I admire is:
"Be careful of what you wish for, it just might come true."