justmuddling mate sometimes you will shout, sometimes you will feel fed up with it/them, sometimes you will wonder why you have put yourselves through it!! But all of these things are COMPLETELY normal. I have two kids so far and try my best not to be a shouty mummy, but sometimes when I'm exhausted and they are both playing up and I haven't been to the bog on my own all day and not finished a single cup of tea, I snap or shout at one/both of them. And feel awful afterwards, and it reminds me why I don't want to be a shouty mum! I just say sorry for shouting and explain why I'm feeling in a cross mood and then suggest we all have biscuits to cheer ourselves up. I think it's important that kids realise that their parents are human beings too.
The fact that you are worried about these things at this stage simply goes to show how anxious you are to do as good a job as possible at being a parent. I have had to take my 4 year old home early from parties because he has misbehaved, and I have seen countless other parents have to do the same, honestly, once you are a parent, everyone is in the same boat and anyone looking at you if your kid is having a strop will just be thinking, "dude I've been there!" And if they're not then they are just being judgemental dick splats (copyright Pirates).
It can be overwhelming at times, being a parent is the biggest, bravest thing I've ever done and at times I've fantasised wondered what my life would be like without them, but I always come to the same conclusion - it would be worse off xxx