How do you keep your cool with 3 year olds

I’m losing my sh*t. I have 3 year old twins and I just don’t know that I am doing a good, or even an okay, job being their mom. I try not to yell and to practice positive parenting, but they just make me repeat myself so.many.times. Or they do things that make me think, wtf? I feel like a ticking time bomb. I yell everyday and I’m snippy with them almost all day long. I feel awful. I love them to pieces but they drive me nuts. They deserve better and I’m just not sure how to give that to them. They’re so sweet to me and so happy. I just feel so guilty thinking that’s all on their own, I’m not doing anything to make them as happy as they are. They’re truly just great little people acting their age and idk how to control my temper.