Dreaming is something we do when we are sleeping, or when we are so tired we are not with it, or people often refer to it as something you will never actually achieve: In your dreams!
Dreaming is such a lovely state of mind, really, if we let our minds take us wherever is necessary. There are many books and websites interpreting dreams, but be careful, because dreams are in context and are very personal.
Hopefully there is some way to always see the dream as positive and turn it around.
Sweet dreams is still a lovely thing to say to someone heading for bed. Just before I say “sweet dreams” to my daughter I say (because she asks or is having trouble sleeping): how about you dream about running as fast as you can through a field full of flowers, bounce on the clouds, fly through the air, or sail on a mushroom in an ocean full of fairies.