"And the servants and officers stood there, who had made a fire of coals; for it was cold: and they warmed themselves: and Peter stood with them, and warmed himself." (John 18:18)
It really won't work, you know. For the child of God, there is never any real warmth at the enemy's fire. Personally, I think Peter could have stood next to that fire till noon of the next day, and still been as bitterly cold as he was on this night. The problem was that he wasn't cold to the bone; he was cold to the soul. That's why, by the time the rooster had crowed the third time, he was reduced to pitiable tears (Matt.26:75).
Christians who find themselves drawn to the exciting flames of this world receive a rude awakening. There will be neither heat nor light for them. Instead, he or she will just end up just getting burnt. The fire of God will warm the inner man...but not the flesh. (Luke 24:32)
I guess it all depends on which of the two you're trying to heat up.