How do I keep smiling at work even though I'm not confident nor content with life/job?

I try to force myself to smile but it doesn't work and just looks worse. I don't really like my job and it doesn't help that I don't have any friends outside of work and its just me alone all the time (been this way for a lifetime). I can't even find anything to talk about with people at work to pass time or if I do try, it ends pretty quickly and there is just no connection/rapport.

I'm concerned that my lack of enthusiasm is showing. Society is made up of 90% of people who aren't passionate about their work yet they still manage to laugh.

I also have post traumatic stress disorder so I'm confused about what is the ailment in all this muddle.

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official