David,
Perhaps the fact you are regretting having wasted time, is because the
things of the earth are not important to you any more.
I have noticed that I have lost interest in a lot of things I use to
enjoy. I have not watched a TV program in a long time. If I do
turn the TV on, it is to watch the News, or the Weather.
I do not watch it (the TV) to be entertained.
I use to love to sit in front of the Television, but the programs now
are just to raunchy.
I think that God is preparing us for the coming of Jesus. That
is why we are losing interest in everything here. He is slowly
weaning us from the things here, and we are longing more, and more
for the things there.
When that trumpet sounds, we will be willing and ready to go.
Not like Lot's wife,  looking back with regret.