Hmm. If anyone can answer this they will win whatever the equivalent of a Nobel Prize is for theology!
I am partial to the first order solution provided by the some Calvinists (no surprise, since I'm one of 'em) who, contrary to the accusation they they deny the free will, actually have the most libertine view. To wit: you will always choose according to your strongest desire at that moment. They don't deny free will, they deny self-denial. You don't want to pay taxes, but you pay them, because at that moment your desire to pay taxes and avoid prison is stronger than your desire to risk prison.
They often put it in terms of moral ability or moral inability. So before God converts you, you have no desire for God; you have a moral inability to choose God. After he converts you, you have a desire, a moral ability, and you choose God. (Yes we Calvinists do actually claim that the elect choose God).
This view of free will is a form of determinism--but not God the puppet master, rather your will is self-determined. You are a slave, not to any external force, but to your desires.
Here is a crude example of moral inability. A mother, with no mental illness, and no extraordinary circumstances, is sitting in the kitchen with her infant. She has free will. There nothing stopping her from putting her child into the microwave. But she literally can't do it (even though she has free will) because she is morally incapable.
So in this view sanctification is some sort of bootstrap wherein through prayer and grace your desires are changed, and then your actions follow along lockstep.
This view breaks down in 2nd order, in my opinion, and I don't know how to fix it, but it is still the best I can grasp.
Now, here is a strong opinion that I'm guessing many will disagree with. There are three generic views of free will:
A) Deterministic (the universe's differential equation is marching along time step by time step.)
B) Theistic (whatever free will is, it's a supernatural gift.)
C) Compatibilism (The non-supernatural belief that free will and determinism are compatible.)
In my opinion, which ain't worth much, one of these is dishonest. That would be C. (The answer is always C.) Take a look at what Dennett says:
The model of decision making I am proposing has the following feature: when we are faced with an important decision, a consideration-generator whose output is to some degree undetermined, produces a series of considerations, some of which may of course be immediately rejected as irrelevant by the agent (consciously or unconsciously). Those considerations that are selected by the agent as having a more than negligible bearing on the decision then figure in a reasoning process, and if the agent is in the main reasonable, those considerations ultimately serve as predictors and explicators of the agent's final decision.
This is, in my opinion, utter woo, as much woo as any religious woo, but it is given a free pass because it sounds a bit sciency. But there is no mechanism for how this magical consideration generator produces nondeterministic considerations.
Edited for typos.