The one time I should have been shy after my own repairs, I wasn't. And I was damned lucky.
For some dumb reason in the late 1970s I thought it might be a really good idea to run my wheel hub bearings on just WD-40 and no grease. Less rolling resistance or some boneheaded logic. First time I felt the heat waves coming off the front hub when I reached down to flip the quick release to lock up the bike, I realized something was desperately wrong with my reasoning.
That afternoon I bought a tube of Phil grease and redid both wheels and the crank before the next morning's commute. I was just lucky the raceways weren't scored.