Hi, how old is dd? Is she neuro-typical?
Don't beat yourself up, it's really tough and little kids can be surprisingly irritating.
You mention "proper discipline" - I don't think you want to train her only to behave nicely when you control her through threats and punishment. But that doesnt mean no consequences; sanctions work when delivered calmly and instantly, so that is usually removing them from a situation or taking something away.
A full-on tantrum is an emotional storm, and your DD has no power to be rational whilst that's happening, so you need to help her prevent thr tantrums.
Start gently etting behaviour expectations before you go out (not with threats but talking about what nice behaviour is like).
The tantrums are caused by big feelings she can't handle, so talk to her about the big feelings and help her recognise them and start to teach her some ways to calm down.
Always gently praise her when she does something good, don't go over the top with it, but make sure you notice when she takes turns, or shares, or stays calm when she doesnt get her own way, or brings you her hairbrush when asked, or puts her coat and shoes away, sits nicely for dinner, listens well for a story and so on.
So i would persevere with the positive parenting because it does work.
Shouting should be reserved for stopping them doing something dangerous but the vast majority of parents lose their temper occasionally. You just pull yourself together and try to do better next time.
When you say you are trying to do lots of nice things, maybe that's the part to tackle so you are doing less ambitious things, closer to home, and then when you feel overwhelmed it is easier to abort. You can build up slowly.
Aim for one special event each day maxiumum and incentivise good behaviour with a sticker chart. Special events can be very low key, short and repeated often.
Kids love doing things over and over and anything she likes, she will behave nicer to get a chance to do it again. Boring for us adults, but excellent training for her! And done well, a sticker chart is a bizarrely powerful tool.
Try and tag team - a playdate with a friend asking the mum to stay for coffee (you're less likely to shout with adult company).
Do you have a garden or access to communal garden?
Some good things at this time of year are:
- planting some seeds /digging for worms (getting muddy is essential)
- having a teddy bear picnic
- washing the car/windows outside (getting wet is essential!)
- going to a local playground. (This is my exception; in summer, most days of the week with little ones i would walk to the playground nearby and just stay as long as I can bear it)
- walking in parkland
- feeding ducks
- finding a kids sports track and going for a scooter/run/cycle
- nature trail (easy to find a seasonal list online, depending on age you can write out the words or draw pictures)
- indoor games like hide and seek
- go to the supermarket/local shops but keep it short and make sure she has her own list of things to shop for, put baby in a sling
- draw outdoor chalk pictures and a hopscotch
- make a pretty card for neighbour and walk to deliver it to them
- jump in puddles, find a place to play pooh sticks, find a place with a huge grassy hill to run down over and over.
I wouldnt make it any more ambitious than that, honestly.