From null to security, a developers tale by Louis Hansen

What happens when a backend developer decides that this Security stuff sounds like a fun area? Well, 4 years later and I can start to give a reasonable answer! Beyond just reading the books, how do you actually transition into Security? What does it mean to switch roles like this? And how much does it suck to start from scratch in a new discipline? (Hint: not at all and a whole lot at the same time!)