There are probably worse moments in parenting, but for me, few outweigh that of holding a vomiting infant.
Sure, the visual isn't great, but it's the one that gets to me.
They can't tell you what is wrong. They are scared. There's really not much you can do and the danger of something bad happening, say suffocation, seems pretty high, since they can't rollover.
The other night, Gianni was in that predicament and I found myself first up with her for 3 hours at 3am and then, sleeping on the floor in her room (as did the NFO, we took turns), just trying to make sure nothing really bad happened.
Fortunately, she seems better now and the "night journey" has passed, for now, but of all of the moments, this is one of the toughest.