Not lonely at all. Many people have other people in their life. While living with others with which one has close and loving relationships and having people with which one can share their thoughts and feel safe may be a condition under which one does not feel lonely. This can be the case for both someone that is convinced that there is a God and for someone who is not convinced. What might be lonely is if someone were unable to express their thoughts or share their experience with anyone else. Imagine if you were the only person that had seen the night sky among a group of people*. It could feel lonely to be unable to find anyone else that has ever had the experience or unable to find someone with which to express your thoughts about it.
- a scenario that might not be as far fetched as it sounds. Where I live and in some other cities the sky has a continuous orange haze on a clear night due to light pollution and high humidity. Unless I drive a considerable distance the night sky doesn’t look as grand. To date I’ve only met one person that has ever been in an area where the Sagittarius arm of the Milky Way could be seen with the unaided eye.
I think that by being human most of us are able to feel the same emotions and our differences here may only be in our semantics when describing these emotions under various conditions. I myself would reserve the use of “gratitude” unless talking about my disposition to someone else for their kind actions (ex: I might have gratitude to a person that brought me cold water on a hot day). Whether or not I got that cold water through someone else or acquired it on my own I would appreciate the cold water (as in finding it enjoyable and good). There is some overlap in usage of “appreciation” and “gratitude” (one could have appreciation for a person or a relationship). Where there is no person thought to be involved I don’t use the word “gratitude.”