Re: Shingeki no Kyojin by ISAYAMA Hajime
Sama_al_Azraq has a point, Eren's transformation probably needs some purpose to happen besides his simply injuring himself. That's one thing. The other thing is obviously emotions. He needs to be under the influence of negative emotions, more precisely hate (that's how he transformed inside a titan's belly for the first time), or suspicion, distrust and animosity, I think.
Inside the well he knew he might get killed if he lost control, but he didn't feel animosity towards his squad-mates for what they would have to do in that case, as he knew they would kill him not out of their personal hate for him but out of duty.
But it all changes when they're relieved he failed to transform. Now, it's rather obvious Eren is not the logical type, but the emotional one, he feels before he thinks, and he rushes to act based on his emotions before even thinking about stopping to analyze the situation first. When his squadmates expressed their relief, I think he sensed their veiled hostility for him. He is being who he is, I doubt he could realize with his mind what their phrases and behavior entail, but I'm sure he felt with his heart they weren't completely honest with him, putting up a friendly facade instead, but in reality they're afraid of him, deep inside they think he's a freak and should be avoided or maybe even dead if possible. They don't really want to accept him the way he is, and, in fact, they're not much different from everybody else who wants him dead. A less extreme point of view, but still basically the same. 'If they're hostile to me, I will be hostile to them.' I suspect he transformed responding to the negative emotion their true view of him stirred in him.
They want him to trust them, yet they're afraid of and don't trust him. Definitely not a situation where I would want to put my life in their hands. And Eren was pretty quick to make his choice after Rivaille's words (he was ready to go fight alone, choosing to trust himself) until Petra called out to him. Then we got that flashback that represents his doubts about trusting them and the evidence not to do so, so to speak.
So far, Rivaille and most likely the crazy scientist are the only ones who don't seem to secretly resent Eren for what he is.
My opinion, anyway.