User blog comment:IamJakuhoRaikoben/Sorcerer Magazine, Issue 3: March 2012/@comment-67.177.209.211-20120403203124/@comment-4449950-20120404000405

Hemhem...*prepare for the rant people* :D

Lucy learnt that her past is not something she should run away from. She had run away from home and hidden her past inside her to avoid people judging her over what her name was/who her parents were/how much money she had. By doing so, she wasn't facing it, rather, she was trying to escape. In the PL arc she learnt that just because she has such a title, those close to her had come to love her for who she was, not what she was. She then faced her father to tell him just that: that she was not going to be the person he wanted her to be, but her own person.

Erza is sort of the same. She tried to hide her past too, but where Lucy acted as herself around others, Erza donned her armour in an attempt to look strong and formidable. She wasn't. Her past was constantly there in her mind reminding her of her inability (no matter how strong she was) to protect those she loved. And so she sealed all of her feelings in her armour and put on a tough face so that no-one would ever question her honour/ her strength. But by doing this she appeared cold and distant. The others helped her realise that her past was not something she needed to handle alone, moreover, that she would be stronger if they were there to support her and help her carry her weight. This is also why Jellal is such an important character. She still feels uncomfortable talking about her harsh past to many people, but he was there with her and experienced first hand everything that she did. He is the one person who probably truly understands her. There is also visual proof. Since the ToH arc, Erza wears her armour less and less in public situations, hinting that her need to wear it due to her past is decreasing.

Gray is a little harder. He had sort of accepted his past; accepting that it was really his stupidity that caused Ur to lose her human form. He did this by taking her advice and living his life to the fullest (heading west and finding strong Mages in Fairy Tail), but he always had a feeling that he was truly at fault and would never make it up. Where he believed he had moved on, Lyon came and shoved everything back in his face. He was forced to once again have to accept things the way they were, which was harsh for him, as he had believed he had already accepted it. He had believed his life to be insignificant, and would have done anything to make up for it (Iced Shell here) but afterwards realised that Ur had not sacrificed her life for him to feel bad and try to repent, rather, she had done it to rid him of the darkness in his heart, so he could be a kind person and live his life to the fullest, which he is currently doing.

Happy has already been stated and I can't be stuffed typing for him...

...and Natsu has no character development (yet - I hope) so I have nothing to say about him...

....gomen > <" and sorry if my English ain't that great. I should have typed this in a more philosophical and inspiring way...but I just woke up....sleepy...