Bad things will happen and you must be ready for them.
A cutaway is inevitable. While there are a number of things you can do to minimize the likelihood of a malfunction, it cannot be avoided altogether. No matter how good your packing technique or how flawless your body position, one day you will experience a major malfunction and you will have to ride your reserve. It is only by internalizing this unavoidable eventuality and by learning to tell a nuisance from an outright equipment failure that you can ensure your survival.
Moreover, understanding that bad things will happen also means preparing for the consequences. Cutting away usually means losing your main canopy and the hundreds or thousands of dollars you've invested in it. Cutting away also has a set of risks that must be evaluated whilst dangling from a malfunctioning parachute: altitude, decent speed, possible canopy entanglement, landing pattern, RSL or no RSL*? These are all factors that have to be considered and rehearsed in detail before you get on the plane.
Wise, measured preparation and swift action under pressure are all that separate a reminder of your mortality from a demonstration of it.
* A Reserve Static Line and it's sibling, the SkyHook, are safety devices built into some parachutes that automatically deploy the reserve canopy in the event that the main canopy is jettisoned. There are good reasons to have them and good reasons not to.