I learned "the hard way" about torquing to spec. Right after I'd bought the E30, I was replacing the factory rotor backing plates with some that would accept hose for brake ducting. I sliced my hand (through my glove) because of a stuck bolt, and wanted to get the job done, quickly, so when replacing the caliper to the steering knuckle, I figured that yanking as hard as I could would generate sufficient tightening torque.
10 miles later, a sickening ka-thunk was heard as the forward bolt bounced off the underbody. Thankfully, I was 500 yards (literally) from a friend's driveway. I got the wheel off and found that the remaining bolt was literally ¼” from falling out. Had that fallen out, the line would have snapped and I would have lost braking (and some clutch assistance).
Now, everything either gets torqued to manufacturer's spec, or in their absence, fastener spec.