what is the most common parenting mistake parents make?

I think the biggest parenting mistake is trying to make your kids learn from your mistakes. I think they need to get their own life experience and learn from their own mistakes or they will never learn at all. :)

I believe that parents make lots and varied mistakes simply because we are human, but the most common mistake (in my opinion), is inconsistency. Unfortunately it is also the most difficult part of parenting. Balancing the fact that you want to make this little person happy and the need to do what is best for him/her can only be done with consistent rules.