Changing your mind in a dream can be a way for your unconscious to tell you that you are approaching a problem in your waking life the wrong way.
If you dream that you change your mind about a friend, it could mean that you should clear up an misunderstanding in your life.
If changing your mind in your dream takes you a long time, you could be irritated by the fact that a project is taking you a long time to finish.
Dreaming that you buy something and then decide that you don’t like it can mean that you are being immature.