Competence or confidence.
Which comes first? Do your ever-improving skills grant you confidence? Or, alternatively, is it your confidence that catalyzes the growth of your skills?
Which came first, the chicken or the egg?
You can certainly have one in spades and suffer a conspicuous lack of the other. Some people are brimming with confidence and have no skills to back up all that bravado. Others have a brilliant array of abilities, but don’t have the gumption to put them all to use.
Sure, it would be ideal to have tons of both. But if you could only have one, which would you pick? Which is a “nice to have” and which is a critical component of your working persona?