How do I stop focusing on the negatives?

Trying to be vague and avoid details so I don’t give myself away, but I recently got a job that required me to move away for an extended period of time. I’m not particularly good at the new job, I’m struggling to adapt to the climate, I work alone all day, and the job site is remote so it’s extremely difficult to do anything outside of the job.

I feel very lonely and angry a lot of the time, and my girlfriend and parents have said that I’m so pessimistic it’s hard to talk to me. How do you make light of situations like this that feel overwhelmingly negative?