The others did not know, but every time Perseus used his power, a certain feedback of it was sent back to his brain, and the pain it came with was only endured by his desire to survive.
However, it is said that little drops of water over time on a stone will eventually break it.
Although Perseus was still a long way from there, he would sometimes sit and imagine the day he lost it and what would happen afterwards.
He wondered if it would break his mind and if he would go on a rampage and probably kill everyone around him.
This subtle fear was not something he recognized at first, but from the first night in this forest, it had started to slowly grow on him.