If you're not happy with your video you can delete it.

Card creators: You'll find a 'Delete contribution' link beneath each video in the card you created. You can delete your own video and you can delete a video from a contributor if you feel it isn't suitable.

Contributors: You'll find a 'Delete video' link beneath the video you recorded. Click the link to delete your video.

If you do delete your video remember that you can record another one.