How do you forgive a parent for not giving you the love and nurturing you needed without an apology?
That's a great question, Alice. And I want to preface my response by saying that even though I'm a therapist, I can't give you a perspective that would be agreed upon by all, or possibly even most, therapists. The concept of "forgiveness" in therapy is very controversial.
As someone who works largely with survivors of trauma, I've found that the pursuit of "forgiveness" is not the answer. I also don't think that "getting over" childhood challenges is the answer either. I don't know what your experience as a child was like, but you obviously harbor some resentment and frustration regarding what happened to you. And for me personally, to insist that you "forgive" or "get over" any of that--that's not fair to you, nor (in my opinion) is at all necessary.
I like to replace the word "forgive" with "cope with". Maybe you'll choose to forgive your parents, but even if you do, acceptance needs to come first. You can cope with what happened when you were a child. Therapy can be a great way to work on coping with neglect, or abandonment, or mistreatment, or trauma, but it all comes down to how you choose to perceive the events of your childhood. I felt a similar way toward my parents in the past. It was hard, but being able to understand that I didn't know what they were going through, that I couldn't appreciate the challenges that they were facing, that was helpful for me. That isn't equivalent to forgiveness, but trying (even though it's so hard when we've been hurt by someone) to understand that some of the pain inflicted upon us really isn't about us at all, but about issues that the perpetrator of that pain is experiencing, that can be a huge step in recovering from what happened.
Anyway, I know there are different ideas about forgiveness, but my personal perspective is that forgiveness is not the ultimate goal, and it certainly doesn't help one to cope with how the mistreatment affects him or her currently. I do encourage you to give therapy a try, not just to deal with the past, but also to move forward without carrying the burden of what transpired when you were a child. If I can help at all, or if you have any further questions for me, just let me know.
Take care,
Nick