If you break one part of God's law, you are guilty of all of it.

"I'm a good person." does not make the grade with God. God calls that self-righteousness, and He knows the intents of every person, you and me included. He must have only those who have been washed clean, and He provided His own Son, Jesus to do the cleansing. Some people think that they are pretty good, but God knows that all have sinned and fallen short of His glory.
Check out this list. Have you ever done any of these things?
If you have even entertained a desire to do any single one of them, you have earned hell and need God's forgiveness.
Judging anyone else when you are not perfect
Telling a lie
Gossiping
Saying a word of contempt for another person
Wishing bad things to happen to others
Holding anger toward another person
Stealing anything
Feeling bad that someone has something that you don't have
Not realizing that God is in control of everything
Not realizing that God is good and perfect
Doing anything that dishonors God
Treating your parents in a way that does not reflect perfect respect and honor
Loving pleasure more than you love God
Loving anything more than you love God
Not believing that Jesus is God's Son
Not receiving Jesus, God's Son
Killing or hurting any person (including the unborn)
Working on the Sabbath Day
Taking anything that does not belong to you (even a piece of paper or a pencil)
Desiring someone else to take something from someone else by force and give it to you. (socialistic programs)
Any promiscuity or perversion. Using that which is holy in marriage in some other way.
Believing worldly sources of information.
Adding to or taking from the Bible by rationalizations

And that list is just the beginning. All have fallen short.
Romans 3:23
Habakkuk 1:13
Isaiah 64:6
Revelation 20:10-15
Isaiah 59:2