How many times a day should you do deep breathing for anxiety? and for how long?

There's more to it..: You can breathe more correctly almost all the time. Shallow is never as good as full and the exhale is what we often get wrong. Completely empty the lungs to remove "old" stuff and make room for refreshing new oxygen. Sometimes 1 or 2 deep out-breaths - even a big groan or shout helps. Try a few cycles of 4 secs nasal inhales, 7 sec hold-ins & 8 sec full, slow pursed lip exhales. Let it be a habit.