Hearing about, being the belayer that did it once and witnessing a near disaster yesterday I am now taking a 70M rope whenever I go climbing. I am also tying a figure eight knot in the bottom end of my rope on every pitch. It is such an easy thing to do. I also double check harness, belay devices, anchors, everything that could have been done wrong. I no longer trust my partner or myself to do it right every single time. These habits have saved my life and friends lives on more than one occasion over the years.
It is all fun and games until it goes bad. So take the time and double check everything and tie a knot in the end of your rope if you are not tying in.
Over the years I have been climbing, I have seen big errors caught by double checking three times. Closing the system all the time (i.e. tying in to the other end of the rope, putting a knot in it, etc.) is super helpful to help avoid accidents. I still use 50 and 60 meter ropes a lot; in this case closing the system is even more important.
Double checking raps is equally important, and having some sort of backup in place adds an extra layer of security when rappelling.
Sometimes with all the double checking it becomes very very very easy to see what you expect to see instead of the hazard that's really there. It takes vigilance to guard against complacency. Complacency is bad shit, it's sneaky too.