I get my parenting advice from a parenting coach who I've known for many years now. He's raised three daughters and all have successfully completed college and entered their dream career fields. As a parent that would be a sweet end game, at least for me that feels about right.
Everytime I sit with this parenting pro I learn something new. You might remember the post we did in meeting your children's 7 essential needs well there's so much more from where that came from. Beyond meeting your children's needs you also must strive to communicate at your optimum best! This is hardest to do with little ones and eventual teens, but the mastery of communication in parenting will lead to a much happier life for all involved.
Now for the how? First things first, when your child is frustrated, angry or sad, dont say, "I understand!" Sure, that must feel off, but there's a better way to connect and show that you truly understand. To do this look for the feelings your child's experiencing and share those. For instance, say to your child: "I see how sad that makes you." "You seem really bothered?" etc. etc. These are more open-ended statements that get a child to think about their answer and in turn they feel understood. Often children then answer your empathetic inquiry with a "yeah" or "yes" and that's how's you know they're feeling acknowledged. This small shift works wonders! Saying you simply understand doesn't quite convey enough sympathy to shut a "bad"'situation down.