Catch (one's) breath verb phrase
To take a break to breathe normally after an excess physical activity
Alan caught his breath after hours of climbing the mountain.
The whole crew are catching their breath before before continuing the journey.
To stop breathing for a very short time because of a surprising or fearful event
Margaret caught her breath whenever she saw that horrible car accident.
To take a seat and relax
To indicate the act of taking a short sleep.
The verb "catch" should be conjugated according to its tense.
This phrase emphasize that Christmas takes place once a year time, so you should grab this chance to indulge yourself and be good to others.
I've eaten a little more than usual as today is Christmas and Christmas comes but once a year, right?