If you have left some one, leave them forever, please!
You have no idea how much it took of them to move on, to heal, to forget your memories, to forget how worthless you made them feel, to forget how many times you took them for granted, to forget how they started blaming their own selves for everything that happened, to get out of that torture and trauma, to forget how much of their time and efforts they invested into someone who decided to leave them in half way and walked away.
Do not come back into their lives with your apologies because apologies cannot make them the person they used to be.
Let them move on.
Your coming back makes them weak again.
Please, stop knocking on the doors you don't intend to step in.
One of the happiest moments in life is when you find the courage to let go of what you cannot change.You will find that it is necessary to let things go; simply for the reason that they are heavy. So let them go, let go of them. I tie no weights to my ankles.