Some people use this verse to say that Jesus claimed to be a mere mortal, and if He is sure that He is going to Heaven, 

then we have nothing to worry about. There are also people who use this verse to deny the deity of Christ. 

That man in the scripture, as most others of that time, saw Jesus as a mere mortal, a non-deity. 

Question: Are human inferiorities and sins not taken into account when allowing people to pass into Heaven? 

Here's what Jesus said in Matthew 5:20, “…For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven.” 

Does that sound like everyone goes to Heaven? Nope. Even that man in Mark 17 said , "...what must I do to inherit eternal life? 

n John 6:29: 29 Jesus answered, “The work of God is this: to believe in the one he has sent.” (read the entire chapter for context). 

My take on of Mark 17: 

1) Since the man saw Jesus as a mere mortal, Jesus was chastising hiim for thinking a mere mortal could be a truly good person

     and deserve to go to Heaven. 

2) Jesus was pre-declaring His deity. Then when He rose from the dead, people would see this that this scripture 

     would illuminate His deity, for how could He save us if He was an unworthy human like us?

 

Doing better won’t save us; we each have a filthy past that needs to be forgiven, lest our sins follow us to the Judgment Day. 

Once we have done wrong as lucid adults, we are marked for destruction, unless we repent, and rely on the sacrifice of Jesus to secure our salvation.