In 2014 I dug into our '97 Mazda MPV to fix a coolant leak (turned out to be loose IM bolts, not a HG or cracked head, yay!), bad pinging (blocked PCV valve), and a bunch of oil leaks (original flattened and brittle o-rings for the distributor, distributor blanking plate, PCV mounting plate, PCV blanking plate, and the front camshaft seals).
I stupidly forgot to tighten the driver's-side cam gear bolt, and the gear walked partway off the cam before shearing the Woodruff key.
The end of the camshaft did not protrude far enough for me to be able to remove the remnants of the Woodruff key, and with great trepidation I had to remove the ricker arms and HLAs on that head to allow the cam to be moved forward far enough to get the Woodruff key out.
I was very careful reinstalling the camshaft, using a thick assembly lube, and torquing down the rockers in small increments.
Anyway, I was initially afraid to drive the van, but it ran perfectly afterwards and gave us another 4+ years if service before the tinworm did it in.
All that to say, after a few weeks I quit worrying about my repairs and accepted that I'd gotten it right.