Last time I had a cigarette due to sheer stress was a few weeks ago - long story shorter, I was driving through an unfamiliar city, in a blizzard, in a car that lacked a right side mirror, and I felt lucky to make it home alive. I like to be able to actually see a bit more when I'm driving.
So I had a smoke, mostly as a nostalgia/reassurance thing - it was OK - and then I went back to vaping because it's better.
Most important from my POV is not to flagellate yourself because you "fell off the wagon". Personally, I think the psychology of THE BIG QUIT is a significant problem; people have a cigarette or three under stress and then convince themselves that they've "failed". Bigger picture; how much were you smoking before you started vaping, as compared to now? For me, I'm down from a pack of Marlboro Red 100s per day, to maybe one cigarette a week or one every couple of weeks. Perhaps significantly, I started vaping as an alternative, not in a do-or-die effort to quit smoking; the fact that I effectively have quit was unexpected and more-or-less accidental.