The mind becomes accustomed to making promises that the body is wholly aware it will not keep. This is not dishonesty; it is rather a realization that wisdom and sensibility are inclined to override statements of bravado and unnecessary risk.
Life is lived in a kind of interpretive theater, where the action is often more playacting then real. Spoken dialogue is pointedly more flamboyant than actual intent, probably indicating design but not necessarily likely time scale or possibility. The road to perfection is indeed shod with good purpose, but paving stones are famously superficially very granular and likely to be considerably worn away by constant abrasive activity.
Being honest does no require being truthful, the tongue is quite capable of lying categorically and utterly believably whilst the mind recognizes a completely different reality. Humans are the most accomplished romancers; the whole polygraph industry relies for profit on that generally proven inane ability. Ambiguity is the seed we constantly sow, fabrication the fruit we savor.