optimism n.
What a programmer is full of after fixing the last bug and
before discovering the next last bug. Fred Brooks's book
"The Mythical Man-Month" (See "Brooks's Law") contains the
following paragraph that describes this extremely well:
All programmers are optimists. Perhaps this modern
sorcery especially attracts those who believe in happy endings
and fairy godmothers. Perhaps the hundreds of nitty frustrations
drive away all but those who habitually focus on the end goal.
Perhaps it is merely that computers are young, programmers are
younger, and the young are always optimists. But however the
selection process works, the result is indisputable: "This time
it will surely run," or "I just found the last
bug.".
See also Lubarsky's Law
of Cybernetic Entomology.