There is nothing romantic about heroin addiction and you are wise to step as far away from it as possible.
It's a cliche to tell you that you have a lot of life ahead of you and happiness will come again, in a healthier way, but it is a cliche because it has proven to be true by those who have walked through the pain and come out the other side wiser for the journey.
What helps, I think, is to remain in "reality", not in the "what if's" or "if only's" or "maybe one day". Face what is instead of dreaming of what could be "if only". Keep your balance and keep walking, girl. You'll be okay, even though it hurts right now.
Hugs