The right campfire choice depends on the next danger, not on pride. Upgrade when it changes upcoming fights; rest when the next bad draw would end the run.
Upgrade cards that change breakpoints
Great upgrades add damage, block, draw, energy efficiency, or a key number that changes how turns play out. Cosmetic upgrades can wait.
Rest before forced danger
If the next path contains a forced elite or boss and your health cannot survive a poor opening hand, rest. A dead run does not benefit from a beautiful upgrade.
Consider potions and relics
A strong potion or defensive relic can make upgrading safe. No potion, low health, and a slow deck usually means resting.