Teachers intuitively know that neither their nor their students’ learning is steady and constant, the same day in and day out and moment to moment, consistent from topic to topic. Learning is dynamic, social, and context dependent because emotions are, and emotions form a critical piece of how, what, when, and why people think, remember, and learn.
http://ww2.kqed.org/mindshift/2016/05/31/why-emotions-are-integral-to-learning/