Are you 100% sure that you will go to Heaven when you die?
You can know! You must realize:

1. You are a sinner
Romans 3:10 “As it is written, There is none righteous, no, not one:”
Romans 3:23 “For all have sinned, and come short of the glory of God;”
The reason we “come short” of God’s glory (God’s righteous or perfect nature) is because “all have sinned.”

2. You owe a sin-debt
Romans 6:23a “For the wages of sin is death...”
The Bible speaks of eternal death, which is also called, “the second death.” You must realize that if you die in your sins, you must
pay the penalty for sin by spending eternity in Hell forever.

3. Your sin-debt has been paid
Romans 6:23 “For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.”
God wants to give us the gift of eternal life. Notice that eternal life is not through going to church, being baptized, or being a good
person; it is through Jesus Christ.

4. You can be saved
Romans 10:9 “That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.” Although Jesus died to pay everyone’s sin-debt, not everyone is on their way to Heaven. You must believe in your heart, and ask Jesus to save you. 

Finally, pray and admit to God that you are a sinner. Believe that Jesus Christ shed His blood on the cross for all your sins.
Understand that He is the only one who can save you and take you to Heaven when you die.
Romans 10:13 “For whosoever shall call upon the name of the Lord shall be saved.”