How can I reduce stress and stop being pessimistic?

I tend to worry a lot about everything..I just feel so stressed out all the time. Even small things irritate me, and sometimes it just feels like I’m going to blow up. Also, when I start feeling positive and happy, it seems like something ALWAYS messes that up somehow!

Can you all give me tips on how to be less stressed out and how to just accept things? I feel like it’s really taking a toll on me