Rambam in Yesodey Hatorah 7 writes that Prophets are very special people that prepare themselves thoroughly to detach themselves from this physical world and serve Hashem.
However, we can clearly see that some of them, once finally presented with prophecy and explicit commandments, backed off, tried to refuse or prove their unworthiness and incapability. For example, Moses refused to lead the Israelites till G-d got very angry, Yona ran away or Jeremiah that also thought he was unworthy and incapable of acting.
I'm trying to speculate on the reasons, but can't come up with anything more than they perceived G-d as a human-like partner that doesn't understand them or doesn't know what they have to say and not as all-knowing, all-present, etc, etc.
How their behavior can be explained in the approach of the almighty and all-knowing G-d?