Although there has been quite a bit written on the subject, astral projection is difficult for many people. The main difficulty is the tendency to forget dream consciousness upon awakening. Accordingly, the successful practice of astral projection requires work. However, the idea is very ancient. What sets it apart from a full OOBE is your hazy consciousness during the experience and poor recall afterwards.
Many people forget most of their dreams completely.
Learning astral projection requires a kind of inner mental clarity and alertness. Dreams are a door to the subconscious which can be used for psychological and spiritual insight, and sometimes for precognition. Dream content is influenced by external sounds and sensations. Dreams are also influenced by events of the previous day, by your moods, and by suggestion. The longest dreams occur in the morning.