I’ve found box breathing very helpful, but the defaults in most of the box breathing apps are pretty conservative. I’ve found it has more of a calming effect the longer you can hold the breath before releasing.

This brings to mind another study from the summer: “Slow breathing impacts inter-organ dynamics modulating brain function and risk behavior” (saw it on HN I think). Finding was that “prolonged exhalation increases risky decisions by increasing reward sensitivity”:

https://www.cell.com/neuron/fulltext/S0896-6273(26)00339-9