And because Heaven is a gift, like any other genuine gift, it is not earned or deserved. Therefore, no amount of personal effort, good works, or religious deeds can earn a place in Heaven for you.
Man is a sinner.
Sin is transgressing God's law and includes such things as lying, lust, cheating, deceit, anger, evil thoughts, immoral behavior, and more. And because of this, man cannot save himself. The Bible says you would have to be perfect. Therefore you shall be perfect, just as your Father in Heaven is perfect. God is merciful and therefore doesn't want to punish us.