The lower level of awe is necessary in order to do mitzvos; the higher level of awe comes as a result of doing mitzvos. "Ahavah rabbah" (great love) is a gift from Above; "ahavas olam" (worldly love) is developed by meditating on creation (Ch. 43.) The love called "my Soul I desire you" is loving G-d because He is your life; the love called "Like a son who strives" is loving G-d more than your life. Both are based on natural feelings that are magnified through meditation (Ch. 44.)