Unsure of good title,about changing

It's all different now
I'm starting a new puzzle
and your piece just doesn't fit.
I'm different now
and you can't change that.
Now longer will i dwell in the past
because I live in the now.

I am happy now
so different from before.
You say you want the old me back
well the old me is gone never to be back
and the new me doesn't want you any more
so please let me show you the door.
You aren't what I want
you aren't what I need.
I don't regret this and I never will
so stop telling me I will.

Though I've made stupid mistakes
and change can be scary
I've never done anything so right.