Sweet Dreams?!

They say dreams are the opposite of our real life..
I believe on it..
But there is a problem..
It means what we have dreamt is totally different in real life..
So if we want to have a sweet life, we should have bad dreams?
If we have sweet dreams, it means we will not be able to get what we wish to in real life?
Then, why we always wish others "Sweet Dreams" before we say Good Night?
Is that mean that we do not want others to have a good real life?
This is totally frustrated...


+Who can give me a conclusion about this?+