Messing up a pour is the worst. Last summer, I tried to fix a patio slab with a dry trowel and it looked like a dog's breakfast. The whole thing set up with these weird ridges and I had to grind it down for hours. My neighbor still jokes about my 'textured' concrete. Now I just wait for the right time even if it means working late.
Honestly, @robinm79, I see your point about waiting for the right time, but I kinda think rushing a trowel job isn't always a disaster. I mean, sometimes you get a unique finish that people might even like. Idk, maybe it's just me, but grinding down ridges sounds like more work than just living with a few imperfections. Plus, working late every time seems overkill when most folks won't notice small flaws. There's something to be said for getting the job done and moving on.