I was helping a customer live-debug an assertion failure in an automated test running in a lab. I messed up an attempt to unwind the stack to restart a call and ended up corrupting the process state. Undaunted, I realized that the issue at hand was that one specific API call was failing, so I said to myself, "That's okay if I can't restart the call. I can just simulate the call!" so I patched registers and manually pushed data onto the stack and all that stuff.
And then I stepped through the code,
and it crashed
I messed up one detail:
When virtually pushing the return address on the stack,
I had a mental lapse and subtracted 4 from the stack pointer
even though this was a 64-bit machine and I should have
Due to the stack misalignment,
the code eventually crashed on a
instruction several stack frames deep into the function.
I blew up the debug session not once but twice.
If this happens to you, don't beat yourself up. If you don't blow up a debug session every so often, then you're not debugging hard enough.