Working on reacting in anger

My daughter is my first child she’s almost 18 months. She is obviously at a age where she is testing my patience and pushing her boundaries a lot and I realize I’m reacting in anger and then I feel horrible afterward. I know she’s learning emotions and growing so fast and I need to be more patient. I REALLY want to work on this.

For example her newest fit is diaper changes or getting dressed. She’ll twist and kick and scream during a whole diaper change. So bad she’ll kick her poop everywhere once or makes it impossible to even get a new diaper on. My first reaction is to get mad and I yell. Then afterward when she’s calmed down I feel horrible. She also throws a fit getting into the car seat, but once we get going she’s fine.

Any advice on how to calmly get through stages like this? I don’t want to be a parent that only yells and I need to work on my patience.

Any tips are greatly appreciated. Or even certain parenting books/websites.

Thanks so much.