Have your beliefs about something that you feel/felt strongly about ever done a complete U-Turn?

I’m not talking about religion here (although, providing this doesn’t turn into an arguement on whether there is or isn’t a God then I don’t mind if you want to talk about any changes to you faith in that aspect) but anything you have felt strongly about. Also, what caused the change in your belief?

For example, I once had a discussion with someone on a Q & A site I was on years ago about abortion. She was 100% pro-life, no if’s, but’s or maybe’s. Then one day she came online and told us that her beliefs on this subject had done a complete U-Turn and that she was now pro-choice for the most part. I never did find out what caused her change in belief. She wasn’t an immature or fickle person and had very strong beliefs on a number of different subjects.

Has this ever happened to you or do you know of someone that it has happened to?