At both extremes in the continuum between pessimism and optimism, there is trouble.
The foolhardy extreme optimist might never save a dime and be defeated by the sudden need for car repairs. The extreme pessimist may never buy a car because there will certainly be repairs.
But looking at the world through pessimistic eyes is an outlook that is personally unhelpful and unpleasant to be around. That's because pessimists always expect the worst and act accordingly. "I will never be able to buy a house (pessimism). The system is rigged against me (cynicism). It means nothing anyway (nihilism)."
According to Berkeley Well-Being, a pessimistic outlook is self-defeating because if you believe you can't do something, you almost certainly won't.
To adopt a better outlook, reframe the problem and state the steps to achieve it. "To own a house, I must have a higher credit score, a down payment, and lower debt. What can I do to solve each of those problems?"
Once you reframe, you might decide that you don't want to address the problem, but at least you know what the steps are. Your future isn't just a dark cloud.
Another tactic is to do what you can, even though you may expect the worst. You may never buy a house, but you can pay your bills on time to get a higher credit score and use less credit to reduce debt. That's two out of three problems solved.
Finally, practice gratitude. Look at what you like about your life and relationships. Feel happy about it. Feel grateful about it. Do that every day.