Possibly, but it's true even on a group rather than an individual scale.

I think it also helps to give people multiple reasons for making a change. So for example as a household we changed our diet by only have meat once a week now, combination of health and environmental benefits pushed us to make the change (Could never go fully vegetarian though).

Pushing people to walk/cycle works because you have both environmental/health arguments.

The difficult one is encouraging people to not excessively heat their houses (we should all be turning our thermostats down a couple of degrees), but maybe cost is a factor there.

I'm going out on a limb and say that people are more worried about the quality of their own life than the quality of other people's life. Even if I was confident that the entire globe would impoverish themselves with me, I would still not want to be impoverished.

Besides, we don't have to scupper our quality of life. Nuclear remains on the table, for example. And it turns out thumb-twiddling for long enough has made wind & solar competitive and they're getting better. The biggest win would be cutting down population sizes and that seems to be happening naturally because it enables people to live more comfortable lives.