My God, this doctrine thing gets heady. Many churches today dance around the topic, or pay it lip service, and proclaim it's all about Jesus. But which Jesus? I cannot get away from this nagging question. And the less it's talked about the more troubled I become because where there are questions, there in infiltration from the outside to fill those voids.
I grasp the basic substance of the faith - the Logos, the Word was the 'subject' of the human we refer to as Jesus. That humanity - everything except an independent 'I' - was assumed by the Word. The will is part of our human nature but the subject (the person?) using the will was not like us. We have what Maximum the Confessor called the 'gnomic' will, i.e. the ability to choose contrary to God's will.
Because the Word was the subject with the human will this was not an option. That Word had to 'fight' through our humanity with a pure will and wrestle that human nature into obedience, realigning its original design into submission. Something like that...
The difficulty at this stage is the 'who' of the humanity of Jesus. We are used to a 'who' in the sense of an individual, isolated being free to make his/her own decisions, the captain of our own ship. But it is sin, the Fall, that has separated us and makes us into such independent beings.
Jesus, on the other hand, is a unique person in that there is no separation. His person, his hypostatsis, has no such separation. It is a union of the divine and the human and it is that union that is the person. Our 'person' is the separated individual that is cut off from our original design.
So His flesh is everything that makes us human except for sin, except for that separation. His will, his questioning, his doubts even (I'm sure there is some council where this was debated that I haven't stumbled across yet) are all those things that make us human. All of it had to be brought into submission. Doubt does not mean lack of faith; it means questions which means our nature is pulling on us. The perfect subject will bring such doubts into alignment and purifying them, redeeming them.