One of the most important aspects of having a dog is the ability to handle that dog safely. Dogs need to be handled by humans for various reasons; bathing when they are dirty, removing bugs, being touched by vet and staff, medical emergencies, and just daily needs (walks, grooming, affection). Some dogs accept handling more readily than others. If you adopt a puppy it is important begin body handling at a young age.
However, a frequent mistake people make with handling their dog is forcing affection, 'dominance' or handling. This is a great way to create fear and distrust. Forcibly holding your dog down to clip their nails or putting them in a bear hug, for which they have obvious discomfort, can create a myriad of issues from distrust, learned helplessness, aggression, and avoidance.
Teaching your dog to enjoy handling takes time, patience, and a knowledge of timing and reward to create positive associations over time.
For more information on body handling: