Fire walking is a dangerous stunt. I've never done it and I might never do it. There are tricky variables and too many ways it can go wrong. And remember, this concern is coming from someone who jumped out of a perfectly good airplane. On purpose!
We understand how it works when it works out well. Burned-down wood may be quite hot, but it's a poor conductor. No one—neither physics educators nor "mind-over-matter" spiritualists—ever walks across glowing metal ingots. The difference is that the physics-types know why doing so would be a bad idea.
So-called "self-help gurus" long ago stole this stunt, rebranding it as a demonstration of self-confidence. The get their marks to pay big bucks to sit in a hotel conference room all day, listening to personal empowerment clap-trap.
To "prove" that this nonsense has changed them (in ways other than diminishing their bank account balances), said gurus arrange for a fire walk at the end of the day. The pitch is that with their new sense of empowerment, they will be able to do things that would have scared them just hours ago.
The fire pit is set up and sometime after dusk, participants shed their shoes. They walk across dewey grass en route to their walk across the burned-down embers. (The dew-wetted feet benefit from a bit of Leidenfrost Effect protection in addition to the previously mentioned low conductivity factor.)
Often, everything goes well and the ruse succeeds. Participants are none the wiser in physics but leave with the confidence they can do anything they desire; anything would be easier than walking on fire,
But it doesn't always work out.
A recent Tony Robbins workshop ended with 21 burn victims incuding at least 3 sent to San Jose hospitals.
There's a nice fire walking debunk by Richard Wiseman on my Web Video for the Classroom page.