Why is the grass always greener?

I have a question I need answered. Why is the grass always greener on the other side of the fence? Why are we so hard to please? Lastly, are all humans like this, or are Americans the worst about it?

In the military you see this type of attitude constantly. Everyone is always so excited to PCS and move to a new duty location. You hear things like "I can't wait to leave this shit hole", "I have been here for way too long", and "finally I'm free".

Yet when these same people get to this "new location" they never stop complaining about how their old unit was so much better. Lots of the time I hear soldiers saying that their first duty station was the best of their entire career, yet if they ever go back, it's not the same. For many people they only remember either the really good or really bad parts about the past. That's why you will hear people say basic training was fun. That is a bunch of BS, basic training is in no way, shape, or form, fun. Looking back however it might seem like it was fun, because you are mostly remembering the good parts.

Looking into the future is much the same way. We either have very high or very low expectations about things to come. Then we arrive, pass up that time, and once again look back and say I wish I could do that again or that was the worst experience of my life.

The point of all this is why are so many of us always looking back or worrying about what's ahead. How about we all just sit back, take a breath of fresh air, and enjoy the moment we are in right now. You never know what the future will hold and you can never re-visit the past. Enjoy yourself now, because you might not be here tomorrow.