Is the heart good or evil?
The heart or the soul/spirit is the real you and Scripture tells us it is more deceitful than all else. It is incurable. There is nothing that anyone can do to cure his sin nature. The only remedy for sin is the blood of Jesus Christ that cleanses us from all of our sins (1 John 1.7; Revelation 1.5).
Everyone is conceived and born in sin (Psalm 51.5) and we all rebel from birth (Psalm 58.3). It is rare when someone seeks God by his or her own free will (Psalm 14.1-3) and everyone goes astray from the way of righteousness (Isaiah 53.6). The only hope anyone has is to have his or her spirit cleansed of sin by trusting in Jesus. Those who trust in Him and in Him alone have their sins washed away and they are given eternal life.
Yet even after a person has his sins cleansed by the blood of Jesus, he cannot trust in his "heart" or his own knowledge, understanding and wisdom. One must trust in God (Father, Son, HOLY SPIRIT). It is only when we totally trust in God and do not rely on our own understanding and wisdom (Proverbs 3.5) that we will make correct decisions.
When we trust in the Lord and acknowledge Him in every decision we make our paths will be made straight (Proverbs 3.6). The way to trust in God and rely on His understanding and wisdom is to study the Bible every day and pray without ceasing.
"The heart is deceitful above all things, and desperately wicked; who can know it?" (Jeremiah 17:9)