Being alone with yourself and your own thoughts, can tend to have influential effects on your own well-being. In most of my experience, being alone has had a negative effect on myself. It's added to depressive thoughts and created a deep loneliness within me. I've had a few too many pity parties for one, alone in my room.
I never thought it would change; never thought it would get better. I told myself I would never be able to survive sanely all by myself.
While you might tell yourself you're a "people person", you must learn how to be alone. If you can spend periods of time alone with yourself, then great. If you can't, you need to learn.
Learning to be alone with yourself will teach you to better love yourself. I don't think anyone likes feeling lonely. It's not a pleasant feeling.
Being able to not feel lonely while being alone is a proud feeling. Knowing you love and appreciate yourself is a feat you should be proud of.