The Lucidity Institue claims:
... many people use lucid dreaming to rehearse for success in waking life. Examples of such applications include public speaking, difficult confrontations, artistic performance and athletic prowess. Because the activity of the brain during a dreamed activity is the same as during the real event, neuronal patterns of activation required for a skill (like a ski jump or pirouette) can be established in the dream state in preparation for performance in the waking world.
German Scientist Daniel Erlacher seems to concur, at least in regard of physical training:
Martin Spies-Sweetland used his lucid dreams to practice long jump. Everything he learns in his waking dreams can then be applied to real life.
Is it really possible that things you learn in a lucid dream can be applied to real life?