Source: Seneca, Epistulae Morales 13.4-5
Source: https://thewalledgarden.com/albert-ellis-stoicism-as-the-root-of-cbt/
Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC4193464/
Source: Epictetus, Enchiridion Ch. 5
Source: https://www.army.mil/article/289608
Source: https://sealfit.com/navy-seal-commanders-advice-developing-mental-toughness/
Source: Marcus Aurelius, Meditations Book 5, Ch. 20
Source: Pennebaker & Kiecolt-Glaser, https://journals.sagepub.com/doi/full/10.1177/1745691617707315
Source: https://modernstoicism.com/stoic-week/