Paul,
It is difficult to go out and 'Sell' to strangers (and selling is what it is) I don't know what your approach is, but it's no good saying to people 'hi, i'm a Carpet cleaner, do you want your Carpets cleaning'?
You have to show people why they need their Carpets cleaning. Even if you don't get in the door on that occasion, at least, if, after you've gone, you have sown a seed in their minds which gets them to ask the question of themselves that they need a clean (the Carpets, not them) it will probably be you that they call first.
Lots of people are reluctant to respond to door to door callers, but if they can go away in their own time and consider what you have said, they just might pick up the phone. You have to appear confident, but not overbearing. It takes guts to do this and nobody likes constant knock backs, but I bet you, that the first time you successfully convert a cold call into a sale it will boost your confidence no end. This will also give you a more positive attitude and will be reflected in how the customer perceives you.
I give this advice as someone who is not a CC (yet) but I have experience in sales (many moons ago) and selling is selling, whatever the product.
Regards.
Martin S