Connecting with people is the most basic aspect of a development professional's work. Cultivating a belief that any interaction could lead to something better--a new volunteer, donation, mention on a popular website, news article--is key to being a successful fundraiser, event planner, grant writer, etc. (Not to mention that someone who hears about a nonprofit's mission may be in need of whatever services it offers or know someone who is, which is also a wonderful outcome.)
I like to keep in mind all the stories I heard as a child where a character who appeared one way turned out to be someone entirely different, such as The Frog Prince or Beauty & the Beast. This helps to remind me, especially in situations like those mentioned above where I don't know the person well, that I should keep my mind open. Fairy tales may sound silly, but there are plenty of stories in real life where surprisingly large donations came from unexpected people (see below for a list of links to just a few such incidences). Of course, those cases don't happen every day, but every day there are opportunities to multiply the impact of modest interactions by viewing them as opportunities.
UK janitor leaves behind $6 million
$10 million to library