Well, I asked mangoisme, and she said I should do this for Finn x Flame Princess. So of course I got right to work.

Guarantee (I find this word painstakingly ironic considering the current state of this pairing)

Their relationship was a tough and rocky one. Finn needed a flame shield to even be around her, and it was only temporary. Flambo was not always available either, so… They couldn't guarantee how long they would last.

Justification

Could they justify themselves? Maybe. But they both knew, that until there was a means for them to be around each other, Finn would continue to search for a way to justify it.

Opportunity

Finn squinted suspiciously at the robed man, holding a scroll in his grimy fingers. "And you're sure this will protect me from burns forever? Without turning me blue?" The old man nodded. Finn grabbed it out of his hand and tossed a couple gold coins in the general direction, running in ecstasy. This was a golden opportunity.

Punishment

Flame Princess was sealed in her lamp once more. After her little rampage on the outside of the Flame Kingdom, her father was keeping her under lock and key. In a giant magical lamp. He saw it as a need for her protection. Her? She saw it as a punishment to keep her away from Prince Finn.

Essence

Fire was made to burn. It was in it's very essence. Did Finn care, as he wore flame proof gloves, stroking his hands through his girlfriend's hair? Nope.