We've all been unsmart (i.e., dumb). Probably more often than we'd like to admit. Being unsmart is not terminal, usually. Rather, it's the starting point for learning something new (and becoming smarter).
The trick is to get through the unsmartness as quickly as possible. Better yet is to recognize our unsmartness and remediate it BEFORE it cost us something we value - like time, productivity, money, relationships, etc.
The real sin, however, is to be unsmart, know we're unsmart, and decide (either consciously or unconsciously) to remain unsmart.
We can put distance between ourselves and unsmartness through self-educating, through seeking out wise and respected tutors/mentors, through purposeful trial and error, and through the reflective process.
It is illusory to believe we can actually achieve smartness. All we can do is diminish unsmartness as often and as thoroughly as possible.
Finally, we must be prepared to face the oft sobering reality that once we have learned something powerful, compelling, and sometimes at odds with what we've been taught and/or believe, we cannot UNLEARN that new thing. That, in itself, can frequently be the most unsettling component of learning.
One of the hallmarks of becoming smarter is the willingness to abandon that which was making us unsmart.