You can love a person for the rest of your life without them being in your life.
we often look to something outside of ourselves to fill the void and pull us out of the state of mind or situation that we are in at the time.
You have to feel the pain of the loss. It could be death of a loved one, the end of a relationship, the loss of a job, or facing an empty nest. Trust the process to get to the other side of your situation.
Depression can be experienced at many levels and for a multitude of reasons and some can't just "snap out of it"
Like alcohol and other recreational drug users can go on a weekend binge or longer, so can sexual behaviors.