How can I cure separation anxiety in my dog?

My beagle has severe separation anxiety. I cannot leave him alone without him howling nonstop for hours. It causes me stress because I feel like I spend as much time as can with him, but I have a life and have to be away from him sometimes for work and school. I am reluctant to get another dog as many people say because I don’t want to risk doubling my problems. What are some good ways to help cure him of separation anxiety, or at leas keep him from howling so frantically?