I have to work to remember to change my white balance setting as I move to new locations and light changes. Either that or I need to start saving my files in RAW format instead of JPG so that if I DO forget, I can easily go back in and edit them. I only recently found out what a major effect white balance can have on your photos. Not only can the incorrect white balance cause your photographs to have an unnatural cast to them, it can also be used creatively to set a new mood for a photograph.
For this example, I thought I would use an example of a recent photograph where I forgot to set my white balance. Thankfully, I had kept the raw format, so I was easily able to go in and alter the white balance.
I love this picture of Matthew, which I posted the other day. The warm glow was part of my love. I think the tones in the photo, blending with the tones of his skin, were what made the photo special. I still had my white balance set up for outdoors instead of for inside with tungsten lighting. Here is the original:
Since I still had the raw version, I was able to go back and 'correct' the white balance to align more with what I had seen with my naked eye.
Notice how Matthew now seems to POP off the page quite a bit more than he did in the more consistently warm-tone original? This is what correct white balance can bring to your photographs. Just a simple correction in the white balance setting can make the difference between a blah picture and one with visual impact.
Since photography is creative, neither of these is CORRECT. It is a personal preference based on what you want to achieve with the end product. It is a setting you can play with, whether the presets already in your camera or setting up a custom definition of white within a setting, that can alter your photography just as much as the exposure.