Having high expectations for chance encounters is gambling and expecting to win.
Meeting someone new and interesting doesn't guarantee you're destined for a new friendship or relationship - it just means you met someone new and interesting. These encounters are opportunities to be satisfied with what is without grasping for more. This must be balanced with being open to what comes next.
Of course if more were to arise from a chance encounter, that would be welcome. The problem is when it's expected.
happiness = reality - expectations