The assurance of salvation has nothing to do with a decision in the past; it has to do with what's going on in the present. - John MacArthur

"One of the legacies that we've had from the kind of evangelism that's gone on in our country is that we believe salvation is attached to a decision, but the assurance of salvation has nothing to do with a decision in the past; it has to do with what's going on in the present. Jesus put it this way in John 8: 'If you continue in My word, then you are My real disciple.' It's always continuous; it's always present tense." 

~ John MacArthur, 
Grace to You Radio Podcast, "Examine Yourselves Whether You Be in the Faith," Part 1.