Treat thoughts like “things will definitely get worse” as symptoms, not as facts

Cost: No cost involved. The hard part is viewing such thoughts as symptoms rather than as objective truths.
In plain terms: In a 20-year twin study, each additional step up on a pessimism scale correlated with a roughly 13% higher risk of dying during that period, and a roughly 20% higher risk of dying from cardiovascular disease. Conversely, higher optimism scores did not bring any comparable benefits. Thus, the focus should be on reducing pessimism, not on simply “being more positive.”
Benefit: This study followed 2,978 twins aged 50 or older in Australia for an average of 20 years; 1,068 of them died over that time. For each standard deviation increase on the pessimism scale, the relative risk of death rose by about 13% (hazard ratio 1.134). The 95% confidence interval for this figure is 1.065–1.207, with a p-value of 8.85×10⁻⁵. Cardiovascular mortality rose by roughly 20% (hazard ratio 1.196; 95% CI 1.045–1.368; p=0.0093). No link was found between pessimism and cancer mortality. Similarly, higher optimism scores showed no meaningful association with mortality rates.
Evidence grade: B
Sources:Whitfield JB, Zhu G, Landers JG, Martin NG (2020). Pessimism is associated with greater all-cause and cardiovascular mortality, but optimism is not protective. Scientific Reports, 10, 12609. https://doi.org/10.1038/s41598-020-69388-y
Notes: This finding remains somewhat controversial. It is purely observational and no subgroups were defined. Some argue that illness might precede and cause heightened pessimism; the authors counter that if that were true, pessimism should also correlate with cancer mortality. Nevertheless, other unmeasured factors could still be at play. Importantly, optimism does not offer any protective effect, so there is no need to force oneself to “think positively.” What matters is refraining from treating pessimistic expectations as accurate forecasts of the future.