Died in vain

I do not set aside the grace of God; for if righteousness comes through the law, then Christ died in vain.” - Galatians 2.21

Why is the doctrine of salvation of grace alone through faith alone such an important teaching? Why is it so important that the New Testament drives it home again and again and again? 

The idea of any kinds of works for salvation is abysmal and blasphemous because it denies the very need of Christ. Paul has already mentioned that works can't save because if they could man could brag about his own salvation. 

But this reason goes much deeper. 

What does it mean if  a man can save himself? What does it mean if keeping the Law, or any other good work, can take someone to heaven? What happens if a religion bases it's tenets on being good enough to placate God? 

What does that do to the purpose for Jesus coming? 

Jesus came to die for sinful man. He came because no one was good enough to save himself. If man could save himself why did Jesus have to come? 

The answer is simple. If man could save himself Jesus did not need to come. The death, burial, and resurrection of Christ were all a waste. Jesus died in vain. 

If man could do it himself Jesus wasted His time. 

To me that is the greatest evidence for salvation by grace alone through faith alone. Jesus didn't come to help man work his way to heaven. He didn't come to fill in the gaps. 

Who are we to think our works could ever be enough to do what Jesus did on the cross?