But there's a quick way out of this situation. Every camera has a menu choice or button combination that resets the camera's controls back to the way they were when the camera left the factory. So exposure, white balance, flash, focus modes, metering methods, image size and quality all change back to settings that will get you good general photos without any bad surprises.
On Canon SLR cameras, look under the Tools menu for a choice that says "Clear All Camera Settings". Even if you don't think you used any Custom Functions, it doesn't hurt to reset them as well. On Canon Powershots (and other compacts) the command is "Reset All".
For Nikon SLR cameras, you hold down the BKT and metering buttons (marked with green dots) for longer than 2 seconds. (This does NOT reset custom functions.)
Other camera brands have a similar choice. Check the camera manual for the specifics.
One thing that does not change is the date and time you have set in the camera. So after you put all the menus and buttons back to their default settings, you are ready to take photos again without any unexpected results and all will be dated accurately.