Day 14 and my dad

So I’m still really struggling with thoughts about my dad. I feel stuck on writing the letter where it says “You told me…” I don’t even know what to put there. I wrote down that he told me that I know what’s best for myself but I don’t think he meant it. And I don’t believe it. I feel terrible for having such awful thoughts or that I can’t come up with anything good to say. My story about him is so negative and I no longer want it to be. How do I begin changing it??