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In photography as in life, sometimes what is needed is to decide on your priorities.
Shooting with the camera set on manual gives you the most control. A lot of your creative decisions involve things like selecting aperture and shutter speed. Modern cameras are fantastic at making many of these decisions for you when you shoot in program or automatic mode. But these settings involve a process of averaging out the various aspects of a given image. When you want something that is more extreme - like a very wide or very small aperture setting or a exceptionally fast or slow shutter speed - photographers need to decide on what making the photo they want involves and choosing the appropriate settings.
You can choose these setting manually for each individual photos. But sometimes you will be doing photos where all the images in a given group will require the same kinds of settings. For example, shooting sports or other subjects where you need to stop motion you will need to select faster shutter speeds. But since lighting may vary from one shot to another you can't just put the camera on manual, select a faster shutter speed and then keep shooting. If you don't make aperture adjustments for each photo you will end up with over and under exposures. But where a lot of activity is involved there often isn't time to constantly adjust aperture and keep up with the action.
You may be in situations in which the best photos involve using a very small aperture for maximum depth of field or a wide aperture to blur the background. Landscape photographers generally shoot with very small aperture settings. But one example of needing wide apertures would be fashion photos, where you want the background behind the model to go soft and out of focus, which requires a very wide aperture. You could be shooting in dim light in which allowing as much light through the lens keeps you from having to shoot at such a slow shutter speed you have trouble getting sharp images. Again, these adjustments can be done manually but that slows you down in situations where you are working with variable light conditions and have to make constant adjustments.
One solution to both these problems is using the ability of your camera to shoot on a shutter priority or aperture priority settings. Using shutter priority, you tell the camera what shutter speed you want to use and it takes that as a constant and adjusts the aperture setting to create the appropriate exposure so you don't have to worry about changes in the brightness of scenes you are shooting that require somewhat more or less exposure.
Using the aperture priority setting, you tell the camera what aperture you want to shoot at and it changes the shutter speed to maintain proper exposure in situations where the amount of light in the scene changes. Your only concern using this technique is that you have to be aware of whether the shutter speed drops to the point where it is too slow to guarantee you get very sharp images.
Remember that with modern digital cameras you have an additional aspect of control that didn't really exist shooting film. You can boost the ISO setting to make your camera more sensitive to light. So if you are shooting and decide you need a smaller aperture than the lighting allows, or you require a faster shutter speed than the automatic settings of the camera can provide, you simply boost the ISO setting so that your aperture/shutter setting can make the necessary adjustments.