A cold shower hands you a clean, timed urge to work with. You plan a minute, and four seconds in every part of you wants out: notice it, breathe, let the wave pass, then notice it come back.

What the research says

Be careful with the claims made around cold exposure and physical challenge in general. A Cochrane review of exercise for anxiety and depression in children and young people found the trials small and of low quality, so confident statements that physical practices reliably maintain psychological gains are not yet supported. Use this because it gives you a manageable urge to practise on, not because the evidence for the cold part is strong.

Strength of evidence: one line of research. A single study, or a theoretical account.