Dear B,
Forgive me for abandoning you. I can't promise that I can give you 100 per cent of myself. I can't promise that I will not leave you again. But I am here now.
I will not give excuses as before we started this it was clear that you needed me to be committed to you.
I am willing to give this another try, though. Let's see how far this will take us.
See you again in a week or two.
Love,
N