In one of my first jobs out of high school it was pretty much door to door sales.... The one guy said to me... this job sucks.. you're going door to door, most people don't want to even talk to you, and when someone does... you still have to close the deal. His silver lining was that, the more doors you knocked on the more chances you have of making a sale (and putting food on the table)
Just think water.... for all those disappointments you've come across, when you finally do score a solid you may be walking around like priapus for a week ....