I still have regrets over what I did when I was 18.
What did you do that you regret?
All the people that I hurt. I really regret doing that.
Sincere remorse can lead to both thankfulness and true forgiveness. If you can make amends for the people you hurt in your past, you might be able to put it behind you and move on.
It's too late now, they will never forgive me
It's never too late to apologize to someone. Even if they don't accept your apology, you can live your life knowing that you did what you could to earn their forgiveness. You can then move on knowing that you did your best to amends for your past mistakes.