Across the cosmos, a breathable atmosphere is an anomaly - at far as we can tell. We are protected from the utter deep cold of space by a relatively thin region of water vapor mixed with oxygen and nitrogen.
The molten core of our planet provides insufficient heat to maintain life on the surface; as such, we are dependent on our parent star to provide the energy required to warm our atmosphere. We are absolutely dependent on a heavenly body 93,000,000 miles from our planet.
Given the above, it seems to me that we live a tenuous existence, and that we as a species are more likely to suffer hardship, even extinction, from a planet that is overly cold, than from one that is overly warm.
A good argument for not squandering our resources.