Character Arcs: Want vs. Need - Common Pitfalls for New Writers?

Hey everyone,

I'm struggling a bit on my latest project, a supernatural thriller, with making my protagonist's arc feel organic. I'm focusing heavily on the 'want vs. need' dynamic, trying to ensure her external goal (saving her sister) directly clashes with her internal truth (facing her own survivor's guilt). I've rewritten the emotional beats a few times, but it still feels a little... manufactured, like I'm forcing the 'need' to emerge rather than letting it unfold naturally.

Looking back at your own experiences, what are some of the most common mistakes you see new screenwriters make when trying to build character arcs based on 'want vs. need'? Are there specific pitfalls that often lead to arcs feeling forced, underdeveloped, or simply not surviving the edit? I'm open to any insights!