Autonomy?

We learned in class that autonomy is self law. Kant believed that good will is pure will and it is from within(autonomy) that we act on this will. What I question is how much of this will is actually autonomy. I feel that I act on things based on my self law, but at the same time it is the influence of heteronomy that it became my self law. For instance(might not be a good example), I choose to hold the door for someone walking behind me because it is polite and is my self law. However, I also know how it feels to have the door slammed in front me and how nice it is when someone holds the door open for me. It is because of this outside experience and heteronomy that I made holding the door my self law.