I remember reading a report about a pilot error.

In most small planes,  the fuel is stored in wing tanks and in many cases,  you manage the fuel balance manually.  General rule,  fly the first quarter of the flight on one tank, switch to the other tank for half, and run the remaining quarter on the first tank.

These folks were on approach and switched off the auto-pilot.  The plane banked hard to the left.   They assumed it was an auto-pilot malfunction,  but they had run the entire flight on the right fuel tank leaving it nearly empty with the left tank tip-top full. The auto-pilot had been managing the imbalance.  Nearly crashed but managed to get on the runway in one piece. 

Little things and simple things can make the difference. I don't fly anymore,  but that was one lesson I learned that saved me trouble down the road.

Thing about flying,  once you take off, you don't get a break till after you land.  There's no pulling over to take time to figure things out.  The old saying is, "A good pilot avoids situations where he has to show how good he is".  True in lots of things I guess.