There is a reason I pay plumbers, electricians and car mechanics to work on my stuff. They're not hacks(usually) like me.
Its funny you mention that. I used to take shortcuts working on my own vehicle when I first started driving. I would put brackets back or wouldn't attach the hoses back to their brackets or whatever it was.
It wasn't until I got serious about it and made it a career that my ugly habits turned around. I'm not in that industry any longer but the "lesson" I learned stuck and I still don't shortcut anymore. It took me doing it professionally for that to change, though. Nothing happened. I didn't have an engine blow up due to something I didn't do or anything like that. I just learned not to cut corners like that because of what could happen.
Somewhat on subject, the only time I ever have given and will continue to give discounted rates to while still giving 100% to the job are for my aging parents when their trucks break down. Because they more than deserve it. I've saved them thousands upon thousands upon thousands of dollars throughout the years because I work for free Having a once-certified service tech on a $0 retainer sure is nice for them. Lol.