George M. Irvine III
Possibly the most important piece of wisdom in the diving world, and is something we should all apply to all of our diving. It is, simply, 'Don't dive with strokes'.

The term 'stroke' refers to someone who, knowing there is a better system, chooses to dive in a less than optimal way. It applies to those instructors who encourage students (who know no better) to exercise personal preference to sell more equipment. It applies to those who don't plan their dives, dive beyond their abilities, dive deep on air, take unnecessary risks, do big dives using unfamiliar gear, or who's only reason for diving is depth.

Diving with strokes moves us into an area where our safety is no longer in our own hands. Strokes are sometimes highly 'qualified'. Often they seem very confident - usually because they have no concept of the danger they are getting themselves, and you, into.
— George M. Irvine III