The phrase 'add fuel to the fire' means when you do or say something that makes a miserable situation even worse. ‘Adding fuel to the fire’ means to make a situation or conflict intensify, especially via provocative comments.
Example of use: "I had plenty to say about the situation, but I was afraid I would add fuel to the fire. So I kept my mouth shut"
'“John only added fuel to the fire when he accused the other team of cheating.”
The direct opposite of "add fuel to the fire" is "douse the flames". This is said when one tries to extinguish or calm down a situation.