i get angry to my child quickly

I want to admit my fault... I get angry with my child very quickly. It's so easy for me to yell at her. I always get annoyed when she has trouble eating or take a long time when we need to go somewhere. I find her very slow. I don't want her to become a spoiled child! Honestly, I'm confused about why I'm like this. Before I had my own child, I had nieces and nephews. I loved them so much, and I was even their favorite aunt. But for some reason, I can't feel the same way about my own child. I felt guilty for yelling at her yesterday when she hid something from me. It turned out she wanted to surprise me for my birthday. But I felt it was unnecessary. By the way, she is almost 4 years old now. Why am I like this...