What is the alternative? If your will is not determined by external determinism (the differential equation of the universe taking its next time step) and it is not self-determined by your desires, on what basis do you make a choice?
On the other hand… I feel your angst. That is why I would say that the self-determinism I described is at most a first order effect, otherwise we are not truly free moral agents. For example, I believe that you can meaningfully pray for God to change your desires–and that the act of prayer is not just itself an irresistible reflection of your strongest inclination as provided by God.
But at that second order–it becomes a total mystery how that works. In my opinion it has to be supernatural.