I have already experience that too, many times. Sometimes it is a signal and a warn to us to do something in order for it to happen. Sometimes they call it subconsciousness, your desire for something but it didn't happen in your plans.
Crying after waking up in a dream seems to be tragic and must be ignore for it reveals messages for us to do something. But dont get annoyed too much sometimes its just a cause of stresses and sometimes cause by the last thoughts you are thinking before you sleep.