Quite simply, this character has a dream that can never come true. This character has been hurt by the world. A lot. Yet despite their pain they never lose hope in their most cherished dream, and even draw strength from pursuing their most fervent desire. Sadly, it's a fool's dream, and not in the romantic Don Quixote sense. It's something that is not just out of reach, but that they are fundamentally incapable of achieving or receiving, and they are usually too emotionally damaged to realize this. They either can't conceive of it as such or avoid the realization because they subconsciously know it would give them a Heroic BSOD. Because of this, the dream stops being something to pine for and becomes a tangible goal they seek, with uniformly horrifying results.