You're in a good place, knowing that you stuff emotions because of parentification. During your childhood, you played a role for the benefit of your dad. In being his best friend, you took care of his needs but ignored your own. Your thoughts, feelings, and opinions became secondary to his. Yet, like most kids in such a situation, you kept it up because it garnered his love, attention, and approval. You didn't know of its negative impact until you became an adult.
Through the years, though, you lost sight of yourself. Therefore, it's understandable that it's hard to express your emotions today. You worry that people will disapprove of you, disagree with you, and use you. Clamming up feels safer.
The writer, Johann Wolfgang von Goethe, said: “As soon as you trust yourself, you will know how to live.” Once you get in touch with who you are, you'll be more confident and less concerned about the reactions of others. You'll feel capable of handling situations as they come instead of worrying about them in advance.
Getting in touch with our feelings and becoming comfortable expressing them takes practice. I have a journal that's dedicated exclusively for jotting down my emotions. I also pause throughout the day and ask myself: How are you feeling? Doing this has helped me tremendously in taking better care of myself (something that those of us who were parentified often struggle to do). Working with a therapist is also beneficial for those who need help connecting with their inner world after years of being disconnected from it.
One of my favorite quotes on being true to yourself is from Dr. Seuss: “Be who you are and say what you feel because those that mind don't matter and those that matter don't mind.” The people who love us won't be scared off when we reveal our feelings. They'll love us even more and appreciate our vulnerability. Those that don't care about us might use our feelings against us. Yet, when we're confident in ourselves, we know that we'll get through it.