This is the 868th most frequent Portuguese word.
próprias
"Próprias" means "own" or "proper" (feminine plural form).
The word 'próprias' is used here to indicate possession and individuality, showing that the shirts belong to the children and were made by them.
As crianças fizeram as suas próprias camisas.
The children made their own shirts.
In this sentence, 'próprios' (plural masculine of 'próprias') emphasizes ownership and personal relation to the fears.
Elas resolveram enfrentar seus próprios medos.
They decided to face their own fears.
Here, 'próprias' is used to stress the uniqueness and personal relevance of the experiences to each individual.