DAYDREAMER is a cognitive architecture that models the human stream of thought and its triggering and direction by emotions, as in human daydreaming. DAYDREAMER includes: daydreaming goals: strategies for what to think about; emotional control of thought: triggering and direction of processing by emotions; hierarchical planning: achieving a goal by breaking it down into subgoals; analogical planning (chunking): storing successful plans and adapting them to future problems; episode indexing and retrieval: mechanisms for indexing and retrieval of cases; serendipity detection and application: a mechanism for recognizing and exploiting accidental relationships among problems; and action mutation: a strategy for generating new possibilities when the system is stuck. DAYDREAMER is implemented as 12,000 lines of Lisp code.