Yearning or relief?

We always sign off saying sweet dreams and usually I have very realistic nightmares...like my passport getting lost...I wake up with a start just to be horribly relieved that it was only a dream. And then there are these rare days, when I have these awesome dreams which contain all the things I can possibly wish for. I wake up with a smile to realise that it was only a dream and as the day passes, every moment makes me realise that I am living a life that does not have what I had dreamt of. Yearning builds up slowly, and there is longing an endstate which I have no control over...so good dreams or bad dreams? I wonder what to prefer?