The gospel is come to you; it has been brought to you. Were you saved because somebody witnessed to you in the office or in college? It was Christ who brought the gospel to you; he sent that messenger; he supervised and superintended that whole interaction.
Assurance need not fade; it need not die away. Of course, it will die away if you adopt worldly ways, if you transfer your enjoyment and desires back to the things of this world, if you are consumed and preoccupied by the here and now, if you lose touch with the means of grace – praying every day, searching the Scriptures, reflecting on these things – you can lose your sense of certainty. But if you sincerely follow Christ, pray earnestly to him, worship him, service him, witness to him you continue to be able to say, ‘I know, I am certain, I am convinced, I am fully persuaded.’