In Purgatorio, the famous tension between fate and free will is explained in terms of love. According to Purgatorio, there are two kinds of love: natural and mental. Natural love is one’s innate attraction to God (whether or not one is conscious of it) and it is fated; man cannot do anything about it, so he is not judged based on his natural love. Instead, his virtue and vice come with his mental love. This love operates by free will. It can target any object of desire. Heaven’s laws, however, require that an individual cannot love unworthy objects (material goods, money) over God, and cannot love anything in improper measure (too much or too little). So if a person exercises free will to err on either side, he can be punished with eternal damnation.
If heaven only “set[s] your appetites in motion,” it does not dictate your destiny. Fate is not an integral part of an individual’s life; the exercise of free will is much more important.
As seen with Dante, fate determines where one’s soul will end up (in Hell or Heaven); fate is thus the key driving force in an individual’s life and there is little one can do to resist it.