Last night’s “How I Met Your Mother” series finale has been met with collective hatred on the Internet. It got us thinking: Has the public ever really liked a series finale? From “Sopranos,” to “Seinfeld” to “Lost,” we really can’t think of any series finale that has not been met with public derision and scorn (with the exception of “Breaking Bad”). We asked our psychogy expert, Art Markman, why.”Television series are different from other media, because they are typically designed to be open-ended,” says Markman. “When JK Rowling wrote the Harry Potter books, she had a story arc in mind from the beginning. When we first meet young Harry, his whole story was wrapped up in the ultimate confrontation with Voldemort. The ending works well, because it is built into the books from the start.”But, a TV series is set up to have overlapping story arcs that carry through for weeks or months at a time that keep viewers engaged and tuning in. “Creating a last episode has a particular challenge, then, because a successful series has engaged viewers with the characters for several years,” says Markman. “The last episode is a chance for the viewers to say goodbye to the characters and to give some sense of closure to the series.”For dramas, such as “Breaking Bad,” it’s often easier to create a satisfactory ending, because there are at least some longer story arcs that can be tied together. “The Sopranos,” on the other hand, was ambiguous and fans were left with a mystery instead of closure.For sit-coms, (case in point: “How I Met Your Mother”) it’s particularly hard. The characters we love are complicated, and the writers had a mere 30 minutes, not counting commercials, to play things out. “So much of the joy of the sitcom comes from the structure of individual episodes,” says Markman. “For that, a finale is difficult, because it is hard to have the episode culminate in a final joke that truly caps off what has come before.”But perhaps the biggest problem is that we will miss the characters. “If we have been following a show for a long time, it is hard to say goodbye,” says Markman. “And so, we have high hopes for the final episode.”It is hard for anything to live up to our high expectations.MORE: Why Change Stresses You Out