Hello and welcome to the parenting stackexchange. I understand it must be some very difficult times for you, and I may not be able to offer as much support as I want, as I do not have the online material and reading needed about non-disciplinarian educations that tend to avoid those tantrum situations.
However, there are several things I think it is worth considering in your case.
As exhausting child tantrum can be, it is a sign of anger, which means there is something causing that anger. While you want to achieve a given goal, for example "changing clothes", there are many reasons a child could be angry (or sad) for the sudden external imperative of a parent forcing the task.
So I would say, it is important to know why anger comes at a given moment. Take care, it might be for multiple reasons, and it might change from one time to another. For changing clothes, I could think of:
- They do not like those particular clothes,
- They were in the middle of a game or another task, and didn't want to be interrupted
- They are tired
To avoid tantrum, it is important to know what actually causes the temper. Feel free to ask, while suggesting where the discomfort might come from ("Are you angry because you wanted to continue playing?" "Are you angry because you don't like those clothes?", ...) Sometimes, you might not find the cause however, but it may be important to persist in case of other tantrums. You should probably avoid expecting answers from the open-ended question "Why are you angry?", as they may lack the intellectual process to fully understand why themselves.
An important thing to consider in those ages is to let the children have some freedom and choices. The particular choice should ideally match the issue that caused the temper. If the child does not like the clothes, give them the choice between various clothes you have chosen. If the child didn't want to get interrupted during its game, offer him some time or point to finish.
Two things to be careful about when giving choices though:
- Do not offer open-ended choices. Before 5 to 6 years, the child might not have enough insight on what possibilities are given, which will put them in a difficult situation. Or they could choose something you don't have.
- Check beforehand that the choices you give them are valid. You don't want your child to choose a given clothing, and later find out they are dirty...
While it seems important to focus on your part on the result, it may be important for the child to understand your need. After all, it is also the case for many adults: we don't like to have something to do when we don't understand why we do it, and we might be angry about it as well.
Take some time to explain why you have a demand. "You need to change clothes because they are dirty, which could make you sick" "You need to change clothes because we soon need to go to school, and you cannot go to school in your pajamas", ...
To avoid the anger that might come from being interrupted, it may be useful to give some heads up. For some time, I took care to tell every night to my daughter what was the schedule for tomorrow. Proposing some time before the task could also work "You need to changes clothes in 5 minutes, before going to school". It may even given some way to give choice (5 minutes? 10 minutes? 2 minutes?)
While I do bring up routines last, it is an important thing to consider. It is often useful to setup routines for some of those tasks. When things go the same way every day, children tend to get used to it easily, and are prepared to the next task, which avoids the anger.
For example, for some time, we had the "evening routine" setup, and we even printed the routine and fixed it on a door with pretty pictures. From memory, it was something like:
- Eating dinner
- Brushing teeth
- Using the toilets
- Getting into pyjamas
- Reading a story
I don't remember very well, but we might have chosen the order together with our daughter. After that, it became really easy to get through all items in order, as long as there was no exception (or exceptions with explanations). And I think after 4 years we still go through the routine without (much) effort, even if it's not printed anymore.
I do not suggest you setup some routines right away, because I think it is more important to understand what the issues are in the first place. But I think it is important to mention it, because your current life as you talk about it seems like a (bad) routine: every day the tantrums. So it is important to break the circle first, to change the current routine.