de-hyperventilate

Refers to what you do immediately following a super-stressful/worrisome period/event (like an emergency repair or tense/uncertain appointment with someone) which you have wheezingly struggled thtough without mishap (thankfully!); you are thus obliged to "deflate and regroup" in exhausted relief afterwards.

I was shaking in my shoes all during my 20-mile drive home due to some malfunctioning of my car's engine, but luckily I did make it back without incident, and then after I'd sat there in my driveway and de-hyperventilated for a few, I checked under da hood to ferret out da issues, and was immensely relieved to see dat it was all fairly-minor stuff dat I could fix myself.