How to I make unholy thoughts go away? I'm scared I won't be good enough to go to Heaven.

Thoughts entering one's mind are common to every person on earth. What you can do to avoid sinning is stopping and diverting your mind into something positive or productive the moment you realise that you were entertaining unholy thoughts. God sees your efforts and knows that you try to stir clear. He will judge you accordingly and not be merciless. However, going to heaven is a long journey based on His grace that showers upon you when you show faith when you are scared, tempted or confused. Live a life that is strong because you act, speak and think in a way that God tells you to. Know God's ways by knowing how Jesus reacted to situations.