Assurance of Salvation

What do you look to for assurance that you will enter Christ's kingdom?  Is there a one-off event or deed that you did to confirm your salvation?  Do you depend on your continued good deeds to assure your place in Heaven?  In this passage, a rich young man who apparently faithfully keeps the Law is still looking for assurance.  Notice how Jesus answers him; it's a lesson for all of us.  From Matthew 19:16-26.