To soften a harsh light source, use a diffuser.
Think about the light of a clear, bright day. It is rather harsh, creating deep shadows and lots of contrast between light and dark tones. Now think about a cloudy or foggy day. The light is softer and more subtle. It appears more even, making shadows slight if at all visible. Why does this happen? The clouds or fog act as a barrier between the sun and the ground. In essence, like holding up a huge white sheet, diffusing the sunlight.
If you need to soften a light source, you can use a ready-made diffuser or make one yourself. Here is a link to my favorite diffuser/reflector combo. If you want to make one, you can use a white sheet, old white t-shirt, or any other white fabric that can let light through. Use white instead of a color. If you use a green T-shirt, the green tint will cast on your subject and your photo will appear off. A diffuser works well when you are outside and the daylight is too bright. If you notice distracting dark shadows on your subject, use a diffuser. Same with a harsh indoor lighting situation. Just hold a diffuser in front of the harsh light, and see how the shadows disappear.
Another trick to softening light is to bounce it. This means you aim your light source towards a surface that will bounce back on your subject. I often use a reflector to bounce light on flowers. I hold a reflector so that the sun catches it, then I direct the light to the flower. Look at the difference between the next three photos. They are the same flower, photographed just minutes apart.
Example #1 shows the lily in harsh sunlight. Look at the dark, strong shadows and white highlights. I didn’t like this lighting for a delicate flower. Example #2 is the lily photographed a few minutes later when a cloud blocked the sun. Better, but no pizzazz. Example #3 is the lily photographed when the cloud parted a tiny bit, giving me enough light to use my reflector to bounce the light inside the flower. This is my favorite shot of the three.
Get yourself a diffuser/reflector combo and your photography will improve by miles.