How far should man's trust in God go? Does the Torah say anything about the relationship between God's Will and man's will? Is there a line where the Torah sees one stop and the other start?
Some of the many views on the nature of the relationship between God's Will and man's will are summarized nicely here. There is one approach that sees God's Will as dominating the universe so absolutely so as to make man's free will and his independent choice impossible. (How can I freely choose if God has knowledge of what my choice will be?) Another view sees free will as dominating the universe absolutely, leaving no space for God's Will (God created the Universe, it's just that he doesn't like to get involoved). Parshat Shelach Lecha offers a compromise of sorts:
The spies have returned from scouting the land and the Israelites await their report. Instead of giving the hard facts they paint a picture that spreads fear and anger through the people. Calev and Yehoshua, two of the spies, are described by the Torah as having responded to the crisis as one, and later, because of their words, are spared punishment by God. Their words are found in Numbers 14, verses 7 and 8:
and they spoke to children of Israel saying: The land, which we passed through is a very very good land. If the Lord delights in us, He will bring us into this land, and give it us; a land which flows with milk and honey.
By linking the success of their military conquest to God's opinion of them, and by describing a project that would undoubtedly require enourmous human effort in passive terms (He will bring us into this land) Yehoshua and Calev express a view that negates neither the dominance of God's Will nor the freedom of man's actions. In short, in these verses the Torah implies a balanced model: Man should do everything in his power to accomplish his spiritual and physical goals whilst remembering that he is ultimately not in control.