You know you should practice every day. How long is long enough?
What should I do when I practice?
Why can't I learn this passage?
Everyone has questions about practicing. When your life is so busy, working and being the taxi for the kids, how do you find time for practicing for the kids or for you?
First of all, let's face the reality. If you don't practice you won't make progress. But also, if you don't practice correctly you won't make progress either.
You should never practice when you are upset. It will just make your practice wasted. Children do not like to be sentenced to a half hour or hour alone in the dungeon to practice. Chances are that practice is wasted. If an adult is thinking about all the other things they have to do or emotional pain they have, it is not likely to be useful.
You must be thinking about what you are doing while you are doing it. A good lesson for any endeavor! Take a little time to think through what you see on the page. Identify patterns, learn to apply theory (how does the melody move, what chord, what cadence). Take the time to play each hand separately to understand what fingering works best for you. Start to hear what the piece will sound like (audiation).
Finally, you may play hands together. Play at different speeds. Play it slowly. Try playing faster and see if it causes mistakes. Try not to make the mistakes habitual. If it is a difficult piece for you, it may take a while to learn it well enough to play faster and accurately. I have had students who played a program for 8 or 9 months to develop the ability and artistry to play a piece beautifully. I once played a piece for three years! If you love the music, it's worth the time.
If it is possible, children need to be in a room where others can listen and encourage them. Be their cheerleader! You go to their soccer and football games and cheer. Do the same for their music practice! People like to do what they think they are good at. If they never get positive feedback from you, they will not want to continue. Remember, it takes 5 compliments to overcome one bad comment. Find positive ways to reinforce correct practice. If you do not allow a child to feel competent, they will not practice effectively. (That also applies to adults!)
If you find you are constantly making the same mistake, analyze whether you learned it wrong to begin with. Once you have practiced a piece with wrong notes or rhythm or fingering, it becomes exponentially more difficult to fix it. You will have to work five times harder to correct it than learning it right in the first place.
In my opinion and experience it is better to carve out time consistently at the same time every day. If you find that impossible, you may be too busy! However, there will be times when it is hard to spend enough time in a day. For times like that I like to just sit down and play one piece. No commitment to an hour. Just play one piece and give yourself permission to walk away. Sometimes that makes a good break from whatever is keeping you busy. It can help you refresh your mind to do what you need to do.
Remember why you started playing! Was it because you love music? Realize that it may take some time before you are capable of complex pieces. But the reward in the end is pleasing your artistic and emotional side. It is worth the effort! Almost everyone can achieve a pleasing level of accomplishment if they are willing to take the time.