Let yourself cry. It's normal, healthy, and necessary. Not having an involved father in your life is a very good reason to shed some tears. The worst thing you can do is bottle up your emotions, (which can lead to depression) or numb them with food, drugs, sex, or alcohol (which can lead to self-destruction).
“Feel the feels” every day by talking about them and writing them down in a journal. Discuss them with a therapist if you think that would be useful. With no intention of ever mailing them, write letters to your father that explain how much his neglect has hurt you throughout the years. This will get you in touch with the little girl you once were and give her a voice to express the anguish.
If you tend to your emotions every day, you'll be less likely to get overcome by them at any particular moment. Contrary to popular belief, getting in touch with our feelings actually makes us stronger. Crying is a beautiful thing and should not be seen as a weakness. You should never be ashamed to do it. It shows you're vulnerable and human.
As a fellow fatherless daughter, I've found it beneficial to pen letters from my imaginary dad to me. In these letters, my idealized version of a dad voices what I've always needed to hear – that he loves me, that he thinks I'm worthy of his time and attention, and that he knows I'll succeed if I'm ambitious and work hard. Since I never heard those words growing up, I find them incredibly comforting and empowering. Here's an example of one I wrote recently:
I want you to know how proud I am of you as you start your new job. I know it's difficult to leave a position that's safe and familiar for something unknown. You'll face many new challenges but are up to the task. I admire you for taking this on and wish you all the success in the world.
This exercise helps me understand what I missed as a fatherless daughter and how it's affected who I am. A good father figure offers encouragement to his kids, pushes them to take risks, and builds their self-confidence. I missed out on all that as a child, but I'm striving to give it to myself now.
Go have a good cry and then keep building a beautiful life for yourself. Take care!