Hafsteinn was born and raised in Reykjavík, Iceland. He graduated with a bachelor's degree in Psychology from the University of Iceland in 2018, and a master's degree in Applied Cognitive Psychology from Leiden University in 2020. Hafsteinn's master’s thesis project was done under the supervision of Henk van Steenbergen of Leiden University, examining the role of touch in cognitive control. Currently, he works at Tübingen University under the supervision of David Dignath.

Hafsteinn's focus in psychology is on human interaction and application in the real world. Specifically, how we humans interact and conceptualize the world around us and how miniscule changes in our surroundings can have drastic effects on our thoughts and behaviors.