Someone said to me once "Relax! Nothing is under control."
Worry about what you can control —which is very little, especially when facing a world crisis like climate change— and accept what you can't.
The people who should be fixing this mess are not you or I. It's the big corporations and the Governments that should regulate them through robust, uncompromising climate policies. Vote for Governments with honest, solid climate agendas.
Other than that, contributions from individuals like you and I are but a drop in the boiling ocean of global warming. By all means, keep doing what you're doing. It certainly doesn't hurt to lead a more sustainable lifestyle but don't feel bad if you don't do everything you're supposed to do. Don't let the real culprits here gaslight you into thinking otherwise.
Again, if you're worried more about your mental health than the problem itself at this stage, it's ok to feel that way. Many of us do. But the best advice I can give you is to just accept there's nothing you can really do about the situation. Whatever happens, happens. Easier said than done, I know, but once you "learn" to accept this fact, your anxiety will drop right down.
The problem with your viewpoint is that it's little more than a thought experiment. Realistically, you will never get all 8 billion people who inhabit this planet to make the necessary lifestyle changes needed to combat climate change.
https://www.wri.org/insights/4-charts-explain-greenhouse-gas-emissions-countries-and-sectors
This one throws has some good figures: https://www.epa.gov/ghgemissions/global-greenhouse-gas-overview
Sources we could attribute to individuals:
In total, 21%. Even if we said that's still a 21% we could do something about, besides switching to a green energy provider and using an EV instead of diesel cars (which is a good move though sourcing the Lithium-Ion batteries these EVs is a big problem in and of itself), what else is there for the average Joe to do? Companies and governments should give individuals the option to lead a sustainable lifestyle. At the moment, the reality is the options simply do not exist or are so expensive that are out of reach for the vast majority of consumers.
On the other hand, we have industrial and public usage...
That's a staggering 80% altogether.
You ever heard of the Pareto principle? It says that 80% of the consequences come from 20% of the causes. In this case, 80% of the emissions come from a minority of people (industry, corporations, etc.).