Plenty of occassions where I doubted I could do it (usually at night when I wanted to sleep instead, but never in the a/c for some reason), but always did, and could never understand why I thought it was difficult afterwards. Now the proud (and unemployed) holder of a CPL/IR and the thought of a simple check ride and VFR nav fills me with morbid thoughts again - wierd! Give me an autopilot and airways anyday.
However, only the instructors were frightened (except for a little incident in a Bulldog following some solo aeros that did leave me wondering whether to bale out or not - talk about cold sweat).