What makes People Lonely?

When I searched "High School Crowd" this was the first image
that was shown. How many people in this picture look like they
aren't lonely? 

I know that I have friends. I know that I have people who love me. So why do I sometimes feel lonely**?
What is it that makes you feel like you're all alone in a crowd of people?
(**These thoughts don't apply to clinical depression. I'm not a doctor and can't give any advice on that besides to go and see a doctor who can help you find hope again.)
I believe that what we need isn't just people around us or even people chatting with us. Mother Theresa said, "The hunger for love is much harder to remove than the hunger for food."
When I'm feeling lonely, the questions I ask are, "Why doesn't anyone like me?" "Why doesn't anyone love me?"

I really enjoyed this video:

My mom also shared that she had been feeling lonely. In church, that week, our Bishop (the leader of our local congregation) stood up and shared that when we feel friendless we should befriend others. When we feel like no one cares we should go out a care for others. When we feel unloved we should give love to others.
Why would that make a difference? There are many reasons, but the one that stood out most to me was this; Heavenly Father is the person who loves us the most. He designed everything for our happiness. When we are serving others we are opening up the door of our hearts so that we can receive His great love.

I know that we can feel that love. He gives it freely and will always give it.