I am talking about messes that serve a creative function. Or messes that teach children about responsibility. I let my daughter get messy and I don't freak out when she makes an unintended mess.
Since summertime has come early this year, I decided to let her to her most favorite thing. Paint the concrete patio outside. I simply pour globs of red, washable paint all over the place and then give her a paintbrush.
Oh, and she does this in her undies. She is a little free-spirit.
I understand for a lot of parents, that it can be difficult to let your hair down after a long workday (or maybe you don't work) and grant your kids artistic freedom. Trust me. I had a hard time doing this. I grew up with strict "no-mess" rules and in the beginning of my daughter's childhood, I enforced those rules.
Until I saw that it hampered her spirit. It hampered her ability to learn from those messes. Most of all, it was stressful.