Taking longer than expected to complete a task can cause disappointment if the expectation constitutes a reference point. In a real-effort lab experiment, I show that a worker's willingness to persevere in a task is influenced by information about task completion time. To directly assess the location and impact of reference dependence, I structurally estimate labor-leisure preferences with a novel econometric approach drawing on cognitive science. This enables preference estimation with high temporal resolution. Once participants exceed an expectations-based reference point or temporal benchmarks along the way, their subjective values of time rise sharply. Workers who fall behind the reference point are demoralized as measured by ratings of task satisfaction.