Failures.
Eren had faced failures in his life ever since he embarked on his journey as a Ranker in the first timeline.
In the past, these failures had left him shattered and made his life miserable. However, he had learned from his experiences and developed a mindset that allowed him to accept failures as a part of life.
Whether he was cursed by the goddess or not, Eren had made peace with the fact that success wasn't something he could easily achieve, regardless of the tasks he undertook or the fields he pursued. This was why he placed great importance on planning things, as he knew he couldn't rely on his luck.
Eren's past experiences had taught him to remain calm even when things were falling apart. It was as if he was trapped inside a burning house with no escape. Despite this, he remained patient, waiting for the house to burn down completely so he could escape. All he needed to do was outlast the flames that were trying to burn him to the cinders.
