Randy's point is well taken. Steel without heat treatment can have anything happen to it and you won't care as much. But after heat treatment, you're working on an object that is close to finished. Starting over on a very thin edge leaves even less room for correction, IF it survives the next cycle through the hot zone. Most will potato chip and become two sizes smaller (8/8 is now 6/8). Or if your tools mean using fire to heat treat, there will be a lot of scale to remove as well. Cleaning all that up, may leave you with no option but to make a frameback out of what's left.
If you're not doing your own heat treatment, you just cost yourself some money in time/postage and another cycle in the furnace.
Then get used to being an example. :) When the steel is hot enough to feel like it's burning your fingers...it's already too late. The heat can still be rising in the material, and fast enough that you can't reach the slack tub where the cooler water is in time to stop the damage to the heat treatment. You may be working the spine, "I was no where near the edge..", and that heat can sweep into the thin sections and you'll know the heartbreak. :( Especially if you can't do your own heat treatment, 'cause that blade is toast and all your work starts again.
For beginners, I'd recommend and repeat, just feeling warm is when to start moving to the water. Don't get me wrong. I admire daring and heavy calloused fingers. But you will get tired of heartbreak fairly quickly, especially when a customer is waiting on a blade to get done and you're on the clock.
Being successful on a grinder means anticipating mistakes before they happen and then not making them. Fixing things after a mistake is a miserable existence.