They aren't opposites, they're different things. My energy hungry lifestyle contributes to global warming and it is comfortable in the short term. What's good now and has been good for me in the past causes something bad in the future. The decline of easy energy is bad for my current lifestyle, and I don't think it can be avoided.
But what would be even worse is trying to avoid the decline of easy energy. Because even if there's petrol and coal and gas left in the ground, we should stop burning it, because we have to mitigate climate change. That's the tragedy.
We're faced with a choice: maximizing short-term comfort by putting back the consequences of reducing available energy, or minimizing long-term discomfort (might be a euphemism) by deliberately cutting down on still available energy.