Increased use of field-based teacher preparation offers important opportunities to develop skills with diverse learners. However, limited focus on theoretical content restricts understanding and generalization of well-proven theoretical approaches, resulting in fragmented field applications unlikely to result in broad application. Inspired by Kurt Lewin's often-repeated maxim that "there is nothing so practical as a good theory," we show how one theory tied to learning and motivation yields coherent pedagogical insights and strategies. Using key theories, teachers can develop approaches for effective use with all learners, rather than requiring a special type of strategy for each type of learner.