To be proud of learning is the greatest ignorance.

Knowing a lot and understanding what knowledge is are different accomplishments, and the second usually makes pride difficult. Anyone who has gone far enough into a subject has met the size of it, and the sensation is less like mastery than like standing at the edge of something. Pride in learning generally means stopping just early enough to still feel impressive. The ignorance in it is not about facts but about scale.

The next time you feel expert, go and find the part of your field you have avoided because it is hard. Spending an hour being a beginner again is the most reliable correction available.