What helps me (some of these things will help you to be calmer, others will improve your relationship to make it more fun and maybe less difficult):
Me time. Self care - not long baths or doing my nails, more like getting takeaway so I don't have to cook or wash up, letting my standards slip on washing the DC's hair or housework etc. Making my life easier however I can, really.
Venting. Have someone non judgemental you can let rip to. Maybe counseling if you have stuff to unpick from your childhood.
Playfulness. Be silly and funny with your daughter, find out what makes her laugh beyond tickling, try to make sure there is laughter and fun and connection between you every day.
One on one time - try to have this with her every day, doing what she wants to do, even if it's just for 10 minutes. Give her a sense of control.
Breathing and feeling your feelings. When you want to lose your shit, breathe for a count of three and ask yourself "is this an emergency?" Observe what your anger feels like in your body and try to see it as a thing separate from you that you can let pass.
Repair - everyone loses it sometimes. Just try to make things better afterwards. Don't leave them. Try to do this as soon after as you can do it with grace.
Allow her her feelings. She's allowed to feel angry, annoyed, upset, grumpy. She's NOT allowed to hit, bite, throw things at the baby. You can prevent these things gently and calmly.
Self forgiveness. Beating yourself up is counter productive. You're doing the best you can even if it doesn't feel like it. You recognise you want to find another way and are working on it. You're a good parent wanting to do better.