As described by Dr. Laura Markham at Aha! Parenting, Positive discipline avoids extremes of marshmallow soft permissive parenting and harsh strict authoritarian parenting by striving to combine kindness and firmness.
To be kind means to validate feelings and show understanding. It can be kind to offer a choice and allow your child freedom in "how" something gets accomplished.
To be firm means to follow through on enforcing the boundary or making the request happen.
Using the word "and" in communicating with children instead of "but" can be helpful.
Here are some examples from the card:
1) I know you don't want to brush your teeth, AND we can do it together.
2) You want to keep playing, AND it is time for bed. Do you want one story or two?
3) I love you, AND the answer is, "No."
The correct balance between kindness and firmness will vary for each child, and even for the same child at different phases of development and circumstances. It is a dance that requires practice and like most of parenting, is best undertaken with a lot of prayer and requests for supernatural wisdom and discernment.