I feel like this was the message the end of Heartcatch was going for, only written and delivered much better and more sensically.
Because yeah, it’s okay to be fueled by passion and anger. Megumi kicked a ton of ass when she was angry people hurt her friend. It’s not a case where you can’t be mad someone got captured or died in front of you.
This isn’t a matter of a sudden hurt causing a gut reaction, but of Iona having been dwelling on this a long time and acting kinda like a jerk because of it. What Iona was doing was not even caring about saving the rest of the world and only fighting to appease her guilt and get revenge. And it was because of this she refused to acknowledge Hime and refused to work with anyone. Iona had no perspective of the scope of this issue and didn’t really care about the fact the entire world was in danger. She shut all that out and didn’t think about the other people who were suffering. That’s obviously wrong and unhealthy, and left her both isolated and reckless for a long period. She DWELLED. She was constantly torturing herself rather than really fighting for what she believed it. Her sister would not have wanted that.
Now she’s realized “hey, I can’t just think about my own guilt. The entire world is in danger and I need to protect it. Other people are suffering because of this too. And I have friends who care about me who want to protect me, so I need to protect them too.” It’s a matter of not becoming bitter and alone and acknowledging the suffering of others and the people you need to fight for.