That person that was laughing, joking, and enjoying is still in you. I've noticed when I feel stuck and have lost enjoyment, there is usually a major concern in my life that is deeply troubling me that I haven't been able to resolve. It makes me feel powerless. I don't always recognize that 'concern' is there unless I spend time asking myself the questions.
Phrysca, I hope things change for you soon. Being a part of a friendship or a workplace can help give a sense of belonging.
