A cliff in a dream often marks a decision point where the next step carries real risk -- a choice you can't easily walk back from once it's made. Standing at the edge can mirror hesitation about committing, while the fear of falling usually names anxiety about what happens if the choice doesn't go the way you hope.
We ought not to use arguments or tedious discourses in giving judgement, much less flatteries, but only to pronounce what is known by experience and firm reason. - Cardan Girolamo (1501-1576)