Katherine Heigl wasn't shy about sharing her feelings about "Grey's Anatomy" (Flickr/friskytuna).

Sometimes, though, actors choose to criticize their past movies or TV shows, in the process insulting not only their fans, but also the hundreds of other people who worked on the project.

In most situations, it’s best that they keep their negative feelings to themselves. Here’s seven reasons why:

It helped your career
When “Titanic” was re-released in 3D last year, Kate Winslet admitted that she’s embarrassed by her own performance. Given that it’s been fifteen years since the movie was first released and its success has helped her become the star that she is today, she might be better off just embracing it. Everyone else loves it.

Well, what else did you expect?
The artistic merit “Transformers: Revenge of the Fallen” was supposed to be irrelevant. A summer blockbuster, a sequel and it was directed by Michael Bay? No one was expecting anything more than a fun action flick to see once and then forget immediately. No one but the movie’s star, apparently. While promoting the franchise’s third installment, Labeouf said “Revenge of the Fallen” lacked “heart,” inducing eye rolls across the world.

People actually liked it
This one should be obvious. If you criticize something people like, it’s not going to go over well.

You might not be better than the movie
Jessica Alba complained that the “Fantastic Four” sequel, “Rise of the Silver Surfer” made her want to quit acting, but many of the movies she’s starred in since, including “Good Luck Chuck,” “Valentine’s Day” and “Spy Kids 4: All the Time in the World,” have received similarly poor feedback.

READ MORE: 'Machete Kills' Packs A Punch With Star-Studded Cast

In fact, it may have been your fault
Acting is a major factor in a movie or TV show’s quality, so actors need to carefully consider their own responsibility before criticizing their own work. When Cher admitted she thought “Burlesque” was a "bad film," at least she was also willing to admit she was dissatisfied with her own performance.

You won’t come across very well
Katherine Heigl became a household name thanks to “Grey’s Anatomy.” She even won an Emmy for her role as Izzie Stevens. Which is why it was so surprising when only a year later, she refused to submit her name for the Emmys, saying the writing she was given didn’t deserve it. When she reportedly stopped showing up for work and was unceremoniously written off the show, it made her seem ungrateful for the show that brought her so much success.

READ MORE: Emmys 2013: The 12 Most Memorable Emmys Moments

No one wants to hear it
If the audience feels a certain way about a movie or TV show, how an actor feels probably won’t change that. It only serves to soothe an actor’s ego to try to prove they have good taste by making disparaging comments about their past work. If an actor is unhappy with something they’ve done, the best thing they can do is try to learn from it and do better in the future.

Reach Staff Reporter Reid Nakamura here.