Sometimes while you write, you come up with two words that you can put down and you say to yourself “Eh, whatever; they are synonyms”.
The words might have a similar meaning, but one might still go better with your work than the other. Think about who is telling the story and their voice – the particular way they put things and why.
Think also of the mood of the story.
You want to describe how cozy your character is on their favorite couch?
Then they won’t just sit down with a blanket and a book, they’ll snuggle in it with a soft/warm blanket and a book.