I was starting back up at the boxing gym (after being out for several months) while
quitting cold turkey.
That was a rough several weeks. Not the cessation, that was easy (2nd time in my life I've done it) - but finding the wind to put in a proper workout even long after beginning to clear out my lungs.
Not holding your breath is excellent advice. Your body will
instinctively compel you toward gasping & retention. Ignore it. Breathe normally
, regularly and evenly.