I have heard that faith can be many things, but what I have been shown in God's Word, faith is very simple. First of all, faith comes by hearing from the Lord God. When the Lord speaks to us He always tells us the end, but does not tell us the journey.
It is in the journey that the Lord tests our faith in what He has promised. An example of this is when the nation of Israel left Egypt. The Lord told them that He would take them to a land flowing with milk and honey. He did not tell them about the journey through the desert and what it would require of them.
Most people give up on the personal promises of God because they do not like how the journey is going for them so far. But, without finishing the journey, our faith in His promises will mean very little.