God has not left us in the dark concerning the most important issue we will ever face and that is to know whether or not we are going to heaven when we die. The Bible (God's only complete revelation of His will) tells you and I in Ephesians 2:8 & 9 "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: not of works, lest any man should boast." When we receive this gift of eternal life, we understand it is a gift. It was not something that we earned or paid for ourselves, even a little bit.
If a friend gave you a $25,000 car as a gift (what a friend!!) and you took the keys and gave him a dollar, it would no longer be a gift. It would be something you paid something for, no matter how small the amount might be.
Once a gift is received, the person who received it should not have to work in order to keep it. The gift of forgiveness cannot be received and then returned. When Christ's righteousness is put to our account, it is there to stay. Listen to what Jesus said in John 10:27-29 "My sheep hear my voice, and I know them, and they follow me: and I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand." John also tells us in I John 5:13 "These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life..".
The wonderful knowledge God has made available to you and I is that we can know and be sure that we have eternal life when we put our faith and trust in Jesus and receive the free gift of salvation.