Where one sits on the pessimism-to-optimism scale does likely affect one's personal response to difficulties - the optimist might have a survival advantage over the pessimist, who we suspect would be more likely to give up and wait passively for the end. A related notion is that the devout religious believer will do better in dire straits than the cynical atheist would, which is an example of the 'utilitarian' argument for religion.
I don't know whether this is actually true in practice. Some people get along through sheer cussedness (which some might interpret as pessimism). I suppose the pessimist more often than not finds reality to be more rewarding than expected - i.e. if you expect the worst, anything even moderately better comes as a pleasant surprise. A similar view is "expect nothing from people, then you'll never be disappointed".
Regardless, reality is what it is. The optimist who leaps off a cliff flapping their arms like a bird, visualizing flight, will come to a splattering end. This is called realism, which should probably take precedence over either optimism or pessimism. Here we can answer the question "how do you know it won't work if you don't at least try?" with a one-liner: math and physics, thank you very much.
As far as fossil-fueled global warming over the next few centuries, I imagine human beings will survive it, but historic disruptions are steadily coming on, and the tipping point has come and gone - there's no going back to the relatively stable, very-gradually-cooling regime of the past few thousand years. We'll see a steadily warming planet for the next 100 years at the very least, there's just no way out of it. A rapid transition to renewable energy is being blocked by entrenched fossil fuel interests (and has been for the past 40 years), and the only countries ahead of the curve are the net fossil fuel importers (China in particular), but even they are nowhere near anything like a meaningful reduction in fossil emissions.
Result? Climate outcomes are heading towards the most extreme of the IPCC predictions. All the bubbling optimism in the world won't change that - it's already here.