If one learns without thinking, one will be lost in his learning. That is, if one does not think about what one learns, he will not arrive at the truth of it.

(idiomatic) to bear in mind

always

to study / to learn

hold, keep (to a limit), suffice / retain, keep, remain / detain, keep, retain

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

mind, heart, spirit, soul; thoughts, ideas / attention, mind, interest / heart, feelings, emotion, emotional state / wholeheartedness, sincerity, true heart

a word, a term / language, speech