Thats our sinful nature makes us evil. When you accept Jesus, it is definitely that you are guranteed with a pass to the heaven but you are still responsible for what you have done. Therefore dont be cheated with a very wrong concept that you will be saved and guaranteed by returning to Christ at the very last moment of your life. Indeed, you have no way to tell when is your last minute.
When you have a chance, come to God and repent to him, acept Jesus as your personal saviour and tell God that you will refrain from what you have done wrong. He is faithful. He does keep his promise to forgive your sin and doesnt forsake you for he is Emmanuel. God with us!
我個人THINK that ,上帝 make a man ,and thought it to the earth for a test, if the man follow his rule ,and he know he is good enought, he will let him/she go to heaven and have joy,
when he is bad, he will let him go to hell