One day you see how old you have become and realise that you have missed the boat; life has passed you by and you will not get a second chance.
In all matters bar one, this is no more than a mere waste. In the spiritual realms however, this is an eternal tragedy. Jesus promises "Seek and you will find." Matt 7:7. This is trustworthy and I know of nobody who has investigated the claims of the Christ openly and honestly who has failed to find Him; discover the reality. God is not an opinion!
As the old time preachers used to dare to say "We are not promised tomorrow!"