Emptiness , not everyone sees people as company for example - introverts , and socializing can be exhausting for them and can be overwhelming for them Or even maybe spending too much time on social media , or not being emotionally available .
This is my personal opinion, So basically you can be around hundreds of people and mentally feel alone because nobody can really relate to you as a person, or really understand you as a person, some people make music to express how they feel towards some situations so people can “relate to it”. Like I’m very known around my city but I feel like nobody truly understands me and I feel alone......
so basically you mentally feel alone but physically be around others.
