Jeremiah 17:5 says, "Cursed is the man who trusts in mankind."
Jeremiah 17:7 says, "Blessed is the man who trusts in the LORD."
These two verses offer a simple comparison in our minds. The one who trusts in mankind, in flesh, will be like a bush in the desert, according to verse 6. No prosperity will be found in this trust. I believe this is talking about true, lasting prosperity. Some of those who heard Jeremiah's words were prosperous to a certain degree. That's one reason why they didn't listen to him, because they felt fine where they were in life. But if we trust in fleshly things we will find no lasting prosperity.
The one who trusts in the Lord, however, will be like a tree planted by the water (reminds me of Psalm 1). When tough times come, there is plenty of water to keep him strong. Why? Because God supplies all his needs! If we trust in the Lord, the Lord has promised to take care of us. And sometimes it looks like we are in tough situations, like we're not prospering. If we don't have a penny to our names here on this earth we are still immensely prosperous if our trust is in the Lord. Trust in the Lord IS wealth!
Nathan