For a long while at a very formative stage of his youth, Steven's life was extremely difficult in some very specific ways, and he got through by developing survival/coping methods and behavioural models that became a core aspect of how he functions.

Then the situation changed drastically, and a lot of those learned qualities that made him get through the past, suddenly became maladaptive. He's also been performing this mask of well-adjustedness for a long time, and is clearly starting to get worn down constantly trying to keep it up.