Learn to be your best friend.

Understand that even though you are on medication you can still be depressed.

You just lost someone you loved. Someone who by the sounds of things was a joy to be around and share experiences with. Someone who helped give your life purpose and regulate your emotions.

A cynical way to look at it is that socialisation draws us out of our own minds and shifts our focus outwardly so we use it as an escape from our current mental state. So learn to be comfortable in your own mind.