The biggest problem is that anybody who posts here saying they don't worry about an engine failure is going to get shot down in flames.
There was even one bloke who wrote somewhere that he was "terrified" every time he flew, and he regarded this as the correct attitude, and I think many would agree.
I cannot think of anything worse. If I was terrified every time I went up I would pack it in and take up
cross-stitching.
The likelihood of an engine failure with a correctly maintained and correctly managed certified engine is very very small. They do happen, which is why one cannot disregard them, and one manages the risk by carrying a life raft, avoiding large built-up areas whenever possible, flying at a high altitude whenever possible (an IR helps a great deal there), etc.
Engine management is important, but is difficult to do correctly in the typical GA rental spamcan context, because there is no or almost no engine instrumentation, so you could be running at a very high CHT and not know it. Thankfully cylinder cracks rarely stop an engine dead. An aircraft owner can install an EDM700, read up on the matter, and never look back. It is a wonderful instrument - if your headset batteries go flat you take a look at the EGTs and if they look normal ...
Fuel management is obviously vital but again is difficult to do in the GA rental spamcan context, because of crappy fuel gauges, and a long tradition in the training system of accepting previous flights' paper log entries as evidence of fuel on board (look up G-OMAR for a super example). Again, an aircraft owner can install a fuel totaliser (the existing gauges have to be left in place) and be precise to within 1% as to his fuel status. I have done 900nm flights and landed within 1 or 2 litres of the FOB which was computed during the flight. Likewise if you suspect a loss of power, take one look at the fuel flow (displayed to 0.1 litre/hr) and if that's OK and the EGTs are OK then the engine is making the power.
The above two things probably take out the majority of engine failures. As for the rest, the best thing is to avoid using UK engine shops
Now I better get off pprune because, according to DFC (oops I meant Mr Guppy) I have a 50% chance of dying today.