I try to take deep 'yoga' breaths. A psychic once told me I am a shallow breather - she was channelling (?) my feelings etc... & told me to take deeper breaths - it might help you? Hard to be aware sometimes of your breath- you really have to be still/sitting to realise if your breath is shallow/fast etc...
What about trying yoga or something like that - I only go once a week but geez I am a much more calmer person & don't really sweat the small stuff anymore. TBH I used to play scenarios in my mind how things would play out/happen & I think this contributed to my stress levels - yoga has helped me be aware in the moment/the now.