I will admit, this one is still very hard for me. I have been working on this since my kids were toddlers and they are quickly becoming tweens and teens. This is an important skill that will grow and change with your kids.
It can be very messy, frustrating or hard to watch. Our instinct is to just jump in and do the challenging task for them sometimes. I would rather just do it then have to clean up a mess after they try to pour the milk themselves, right?
There are times that we do just have to step back and let them learn how to do something for themselves. Often kids will find a more creative way or a more efficient way to do something, if left to their own to solve a problem.
It also helps develop communication. They know how to ask for specific help, rather than just that they need help. This is a huge skill as a learner in school. The more accurate the feedback a teacher has, the more easily a problem can be solved.
It also drives their self-confidence. It can be messy, but when they make cupcakes by themselves the first time, it is fun to see how proud they are. Just like learning to ride a bike, part of riding is learning about how not to fall. The smiles are the reward you get when you give your kids a little bit of space and time to solve their own problems.