Most theories on learning to teach focus on active, reflective learning. In this article it is argued that three sources of regulation have to play a role in knowledge construction in learning to teach: external sources to provide new information, active internal sources to deliberately focus on (new) information, and dynamic internal sources to spontaneously reconceptualize prior understandings. It is suggested that the ability or readiness of student-teachers to effectively involve all three of these sources in their learning may depend largely on how emotionally risky it is for them to change their perception of reality. Disappointing outcomes of teacher education are considered from the proposed theory. Implications for teacher education are discussed.