Jeremiah 17:9-10, "The heart is deceitful above all things, and desperately wicked: who can know it?  I the LORD search the heart, I try the reins, even to give every man according to his ways, and according to the fruit of his doings."
Verse 9 teaches the truth about the human heart (soul) and that it is deceitful (supplanting) above all things, and incurably wicked. Therefore, outside of God and His Word who could know its real condition or state. Barnes' Notes on the Bible states, "...man's heart is incapable of seeing things in a straightforward manner, but is full of shrewd guile, and ever seeking to overreach others." You see the man who is blessed is the man who trust in God rather than in himself. Jeremiah 17:7, "Blessed is the man that trusteth in the LORD, and whose hope the LORD is." The man who isn't blessed is described in Jeremiah 17:5, "...Cursed be the man that trusteth in man, and maketh flesh his arm, and whose heart departeth from the LORD."
The answer to the question in verse 9, "who can know it?" Who can know the condition of the human heart ONLY GOD CAN. Like a cardiologist verse 10 states, "I the LORD search the heart, I try the reins (mind or inward thoughts)." Do you see now why the man who is blessed is the man described in Jeremiah 17:7 rather than the man described in Jeremiah 17:5.
Oh that we will be people who trust in the LORD. God's Word will accomplish it's purposes and will do the job to analyze our hearts and direct us in the correct path, "For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart." (Hebrews 4:12)
Also, may we help others in their wayward lives to trust in the LORD.
Have an enjoyable day being led by the Holy Spirit rather than your desperately wicked and incurable heart.
Your Friend in HIM,
Pastor Mike Abbott