I am, after all, an adult, a grown man, a useful human being, even though I lost the career that made me all these things. I won't make that mistake again.
You can reduce your anxiety somewhat by facing the fact that there isn't a mechanic alive who doesn't louse up a job once in a while. The main difference between you and the commercial mechanics is that when they do it you don't hear about it--just pay for it, in additional costs prorated through all your bills. When you make the mistakes yourself, you at least get the benefit of some education.
"It's suicide," Doc Holland said, shaking his head. "Fools, all of them. This isn't any conventional war- this is madness." The general let out a weary breath. "No, Doctor-this is fear . . . and fear makes fools of us all."