Sri Aurobindo
Letters of Sri Aurobindo
08. Transformation of the Physical
It depends on the connection between the two states of consciousness at the time of waking. Usually there is a turn over of the consciousness in which the dream-state disappears more or less abruptly, effacing the fugitive impression made by the dream events (or rather their transcription) on the physical 
sheath. If the waking is more composed (less abrupt) or, if the impression is very strong, then the memory remains at least of the last dream. In the last case one may remember the dream for a long time, but usually after getting up the dream memories fade away. Those who want to remember their dreams sometimes make a practice of lying quiet and tracing backwards, recovering the dreams one by one. When the dream-state is very light, one can remember more dreams than when it is heavy.